The Wikipedia entry is a good place to start. Since these entries have a bad habit of being changed- especially once the company trolls get wind of them- I'm going to exercise some Fair Use rights here:
...Glyphosate is an aminophosphonic analogue of the natural amino acid glycine and the name is a contraction of glycine, phospho- and -ate. It was first discovered to have herbicidal activity in 1970 by John E. Franz, a scientist who worked for the Monsanto company. Franz received the National Medal of Technology in 1987 from Ronald Reagan for his discoveries and in 1990 received the Perkin Medal for Applied Chemistry. Franz is an inductee of the National Inventors Hall of Fame.
Glyphosate kills plants by inhibiting the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), which catalyzes the reaction of shikimate-3-phosphate (S3P) and phosphoenolpyruvate to form 5-enolpyruvyl-shikimate-3-phosphate (ESP). ESP is subsequently dephosphorylated to chorismate, which is an essential precursor in plants for the aromatic amino acids: phenylalanine, tyrosine and tryptophan. These amino acids are used as building blocks in peptides and to produce secondary metabolites such as folates, ubiquinones and naphthoquinone. X-ray crystallographic studies of Glyphosate and EPSPS shows that glyphosate functions by occupying the binding site of the phosphoenol pyruvate, mimicking an intermediate state of the ternary enzyme substrates complex. The shikimate pathway is not present in animals, which obtain aromatic amino acids from their diet. Glyphosate has also been shown to inhibit other plant enzymes and also has been found to affect animal enzymes.
Roundup has a United States Environmental Protection Agency (EPA) Toxicity Class of III for oral and inhalation exposure, but more recent studies suggest that IV is appropriate for oral, dermal, and inhalation exposure. It has been rated as class I (Severe) for eye irritation, however. A 2000 review of the available literature concluded that "under present and expected conditions of new use, there is no potential for Roundup herbicide to pose a health risk to humans".
In 1996 Monsanto was accused of false and misleading advertising of glyphosate products, prompting a law suit by the New York State attorney general.
On Fri Jan 20, 2007, Monsanto was convicted of false advertising of Roundup for presenting Roundup as biodegradable and claiming that it left the soil clean after use. Environmental and consumer rights campaigners brought the case in 2001 on the basis that glyphosate, Roundup's main ingredient, is classed as "dangerous for the environment" and "toxic for aquatic organisms" by the European Union. Monsanto France planned to appeal the verdict at the time. 
On two occasions the United States Environmental Protection Agency has caught scientists deliberately falsifying test results at research laboratories hired by Monsanto to study glyphosate. In the first incident involving Industrial Biotest Laboratories, an EPA reviewer stated after finding "routine falsification of data" that it was "hard to believe the scientific integrity of the studies when they said they took specimens of the uterus from male rabbits". In the second incident of falsifying test results in 1991, the owner of the lab (Craven Labs), and three employees were indicted on 20 felony counts, the owner was sentenced to 5 years in prison and fined 50,000 dollars, the lab was fined 15.5 million dollars and ordered to pay 3.7 million in restitution. Craven laboratories performed studies for 262 pesticide companies including Monsanto.
Monsanto has stated that the studies have been repeated and that Roundup's EPA certification does not now use any studies from Craven Labs or IBT. Monsanto also claims that the Craven Labs investigation was started by the EPA after a pesticide industry task force discovered irregularities.
Glyphosate itself is practically nontoxic by ingestion or by skin contact. The acute oral toxicity of Roundup is > 5,000 mg/kg in the rat. It showed no toxic effects when fed to animals for 2 years, and only produced rare cases of reproductive effects when fed in extremely large doses to rodents and dogs. It has not demonstrated any increase in cancer rates in animal studies and is poorly absorbed in the digestive tract. Glyphosate has no significant potential to accumulate in animal tissue. 
Not only is glyphosate used as five different salts but commercial formulations of it contain surfactants, which vary in nature and concentration. As a result, human poisoning with this herbicide is not with the active ingredient alone but with complex and variable mixtures. 
A review of the toxicological data on Roundup shows that there are at least 58 studies of the effects of Roundup itself on a range of organisms. This review concluded that "for terrestrial uses of Roundup minimal acute and chronic risk was predicted for potentially exposed nontarget organisms". It also concluded that there were some risks to aquatic organisms exposed to Roundup in shallow water. More recent research suggests glyphosate induces a variety of functional abnormalities in fetuses and pregnant rats. Also in recent mammalian research, glyphosate has been found to interfere with an enzyme involved testosterone production in mouse cell culture and to interfere with an estrogen biosynthesis enzyme in cultures of Human Placental cells.
Studies have shown that the application of Roundup on wheat crops a week before harvesting results in higher glyphosate residue in the resulting grain and in the baked flour. 
The United States Environmental Protection Agency, the EC Health and Consumer Protection Directorate, and the UN World Health Organization have all concluded that pure glyphosate is not carcinogenic. Opponents of glyphosate claim that Roundup has been found to cause genetic damage, citing Peluso et al. The authors concluded that the damage was "not related to the active ingredient, but to another component of the herbicide mixture.
There is a reasonable correlation between the amount of Roundup ingested and the likelihood of serious systemic sequelae or death. Ingestion of >85 mL of the concentrated formulation is likely to cause significant toxicity in adults. Gastrointestinal corrosive effects, with mouth, throat and epigastric pain and dysphagia are common. Renal and hepatic impairment are also frequent and usually reflect reduced organ perfusion. Respiratory distress, impaired consciousness, pulmonary oedema, infiltration on chest x-ray, shock, arrythmias, renal failure requiring haemodialysis, metabolic acidosis and hyperkalaemia may supervene in severe cases. Bradycardia and ventricular arrhythmias are often present pre-terminally. Dermal exposure to ready-to-use glyphosate formulations can cause irritation and photo-contact dermatitis has been reported occasionally; these effects are probably due to the preservative Proxel (benzisothiazolin-3-one). Severe skin burns are very rare. Inhalation is a minor route of exposure but spray mist may cause oral or nasal discomfort, an unpleasant taste in the mouth, tingling and throat irritation. Eye exposure may lead to mild conjunctivitis, and superficial corneal injury is possible if irrigation is delayed or inadequate. 
Fish and aquatic invertebrates are more sensitive to Roundup than terrestrial organisms. Glyphosate is generally less persistent in water than in soil, with 12 to 60 day persistence observed in Canadian pond water, yet persistence of over a year have been observed in the sediments of ponds in Michigan and Oregon.
The EU classifies Roundup as R51/53 Toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment.
Roundup is not registered for aquatic uses and studies of its effects on amphibians indicate it is toxic to them. Glyphosate formulations that are registered for aquatic use have been found to have negligible adverse effects on sensitive amphibians.
When glyphosate comes into contact with the soil it can be rapidly bound to soil particles and be inactivated. Unbound glyphosate can be degraded by bacteria. Roundup has been shown to increase the disease rate in the crop following a sprayed crop, suggesting damaged soil flora. 
Low glyphosate concentrations can be found in many creeks and rivers in U.S. and Europe, and in the US glyphosate has been called "relatively persistent" by the EPA.
The EU classifies Roundup as N - Dangerous for the environment 
In soils, half lives vary from as little as 3 days at a site in Texas, 141 days at a site in Iowa, to between 1 - 3 years in Swedish forest soils. It appears that more northern sites have the longest soil persistences such as in Canada and Scandinavia.
However, the binding of glyphosate to particulates can be an advantage for the detoxification of industrial toxin-polluted streams containing a wide class of toxicants. Treatment of industrial wastewater using immobilized bacteria showed complete conversion of glyphosate to nontoxic aminomethylphosphonic acid.
A recent study concluded that certain amphibians may be at risk from glyphosate use. One study has shown an effect on growth and survival of earthworms. The results of this study are in conflict with other data and has been criticized on methodological grounds. In other studies nitrogen fixing bacteria have been impaired, and also crop plant susceptibility to disease has been increased. 
Monsanto firmly denies any negative impact on anything, including wildlife, and has many studies it has funded to back up its position. They would also be quick to point out that any possible negative impact on earthworms and nitrogen fixing bacteria, etc., would be offset by greater yields, which have not been proven, due to the elimination of weeds, and also would point to soil benefits from less mechanical cultivation of weeds by using Roundup and similar products...
An in-vitro study has suggested glyphosate may have an effect on progesterone production in mammalian cells and affect mortality of placental cells in-vitro. Whether these studies classify glyphosate as an endocrine disruptor is a matter of debate.
Some believe that in-vitro studies are insufficient, and are waiting to see if animal studies show a change in endocrine activity, since a change in a single cell line may not occur in an entire organism. Additionally, current in-vitro studies expose cell lines to concentrations orders of magnitude greater than would be found in real conditions, and through pathways that would not be experienced in real organism.
Others believe that in-vitro studies, particularly ones identifying not only an effect, but a chemical pathway, are sufficient evidence to classify glyphosate as an endocrine disruptor, on the basis that even small changes in endocrine activity can have lasting effects on an entire organism that may be difficult to detect through whole organism studies alone. Further research on the topic has been planned...
But doubtless not funded, except by Monsanto, which has already written up the results for you.
#1 US EPA 2000–2001 Pesticide Market Estimates Agriculture, Home and Garden
#2 Technology Administration Agency, US Department of Commerce
#3 Colby Stong, The Scientist 1990, 4(10):28
#4 Purdue University, Department of Horticulture and Landscape Architecture, Metabolic Plant Physiology Lecture notes, Aromatic amino acid biosynthesis, The shikimate pathway - synthesis of chorismate.
#5 Saccharomyces Genome Database - S. cerevisiae Pathway: chorismate biosynthesis
#6 E. Schönbrunn et al, Interaction of the herbicide glyphosate with its target enzyme 5-enolpyruvylshikimate 3-phosphate synthase in atomic detail, PNAS 2001,98:1376-1380
#7 (Su , L.Y. et al. 1992. The relationship of glyphosate treatment to sugar metabolism in sugarcane: New physiological insights. J. Plant Physiol. 140:168-173.)
#8 (Lamb, D.C. et al. 1998. Glyphosate is an inhibitor of plant cytochrome P450: Functional expression of Thlaspi arvensae cytochrome P45071B1/ reductase fusion protein in Escherichia coli. Biochem. Biophys. Res. Comm. 244:110114.)
#9 (Hietanen, E., K. Linnainmaa, and H. Vainio. 1983. Effects of phenoxy herbicides and glyphosate on the hepatic and intestinal biotransformation activities in the rat. Acta Pharma. et Toxicol. 53:103-112.)
#10 EPA ReRegistration Decision Fact Sheet for Glyphosate (EPA-738-F-93-011) 1993. [.pdf]
#11 Williams GM, Kroes R, Munro IC. (2000) Safety evaluation and risk assessment of the herbicide Roundup and its active ingredient, glyphosate, for humans. Regulatory Toxicology and Pharmacology, 31 (2): 117-165. PMID 10854122.
#12 Attorney General of the State of New York. Consumer Frauds and Protection Bureau. Environmental Protection Bureau. 1996. In the matter of Monsanto Company, respondent. Assurance of discontinuance pursuant to executive law § 63(15). New York, NY, Nov
#13 Monsanto Fined in France for 'False' Herbicide Ads
#14 (US EPA Communications and Public Affairs 1991 Note to correspondents Washington DC Mar 1)
#15 (US EPA Communications and Public Affairs 1991 Press Advisory. EPA lists crops associated with pesticides for which residue and environmental fate studies were allegedly manipulated. Washington DC Mar 29)
#16 (U.S. Congress. House of Representatives. Com. on Gov. Oper. 1984. Problems palgue the EPA pesticide registration activities. House Report 98-1147)
#17 (U.S. EPA 1978 Data validation. Memo from K LOcke, Toxicology Branch, to R Taylor, Registration Branch. Washington DC Aug 9)
#18 (U.S. EPA Office of pesticides and Toxic Substances 1983, Summary of the IBT review program. Washington D.C. July)
#19 Schneider, K. 1983. Faking it: The case against Industrial Bio-Test Laboratories. The Amicus Journal (Spring):14-26. Reproduced at Planetwaves
#20 (US Dept. of Justice. United States Attorney. Western District of Texas 1992. Texas laboratory, its president, 3 employees indicted on 20 felony counts in connection with pesticide testing. Austin TX Sept 29)
#21 (US EPA Communications, Education, And Public Affairs 1994 Press Advisory. Craven Laboratories, owner, and 14 employees sentenced for falsifying pesticide tests. Washington DC Mar 4)
#22 Glyphosate Factsheet (part 1 of 2) Caroline Cox / Journal of Pesticide Reform v.108, n.3 Fall98 rev.Oct00
#23 Backgrounder: Testing Fraud: IBT and Craven Labs, June 2005, Monsanto background paper on RoundUp [.pdf]
#24 Roundup PRO® Herbicide MSDS [.pdf]
#25 Extoxnet Pip - Glyphosate
#27 Glyphosate poisoning study by Bradberry SM, Proudfoot AT, Vale JA.for the National Poisons Information Service (Birmingham Centre) and West Midlands Poisons Unit, City Hospital, Birmingham, UK.http://www.ncbi.nlm.nih.gov/pubmed/15862083
#28 JP Giesy, KR Solomon, S Dobson (2000). "Ecotoxicological Risk Assessment for Roundup Herbicide". Reviews of Environmental Contamination and Toxicology 167: 35-120
#29 Effect of the herbicide glyphosate on enzymatic activity...[Environ Res. 2001] - PubMed Result
#30 Walsh et al Roundup inhibits steroidogenesis by disrupting # steroidogenic acute regulatory (StAR) protein expression. Environ Health Perspect. 2000 108: 769–776.
#31 Richard et al, Differential Effects of Glyphosate and Roundup on Human Placental Cells and Aromatase, Environmental Health Perspectives Vol. 113, No.6, 716-720[.pdf]
#32 WHO Environmental health criteria # 159 http://www.inchem.org/documents/ehc/ehc/ehc159.htm#PartNumber:1
#33 US EPA Reregistration Eligibility Decision - Glyphosate [.pdf]
#34 Peluso M, Munnia A, Bolognesi C, Parodi S. Environ Mol Mutagen. 1998 31:55-9 PMID 9464316
#35 http://lscgw1.monsanto.com/esh/msdslib.nsf/2B20DAEB04E8631C0625689700650B45/$file/Roundup%20Ultra%203000-5059en-gb.pdf Roundup Material Safety Data sheet page 7, heading 16
#36 Monsanto Backgrounder 2005 Response to "The impact of insecticides and herbicides on the biodiversity and productivity of aquatic communities" [.pdf]
#37 Rick A. Relyea 2005 The impact of insecticides and herbicides on the biodiversity and productivity of aquatic communities Ecological Applications 15:618–627
#38 Wojtaszek et al Effects of vision herbicide on mortality, avoidance response, and growth of amphibian larvae in two forest wetlands Environmental Toxicology and Chemistry 23:832–842 2004 [.pdf]
#39 Balthazor, Terry M and Laurence Hallas (1986) Glyphosate-degrading microorganisms in industrial waste treatment biosystems. Appl. Environ. Microbiol. 51:432-34.[.pdf]
#40 CROP ECOLOGY, MANAGEMENT & QUALITY published online 26 August 2005 by M. R. Fernandeza, F. Sellesa, D. Gehlb, R. M. DePauwa and R. P. Zentner.
#41 Adams, William, Laurence Hallas, and Michael Heitkamp. 1994. Microbes and their use to degrade N-phosphonomethylglycine in waste streams. United States Patent 5288635
#42 Bette Hileman. (2005) Common herbicide kills tadpoles. Chemical & Engineering News. Washington 83(15):11.
#43 (Springett & Gray 1992, Soil Biol. Biochem. 24 (12):1739-1744)
#44 (Santos & Flores 1995, Lett. Appl. Microbiol. 20:349-352)
#45 (Brammel & Higgins 1988, Can. J. Bot 66:1547-1555)
#46 (Johal & Rahe 1988, Molec. Plant Pathol. 32:267-281)
#47 (Mekwatanakarn & Sivassithamparam 1987, Biol. Fertil. Soils 5:175-180)
#48 (Kawate et al. 1997, Weed Sci. 45:739-743)
#49 (Bergvinson & Borden 1992, Can J. For. Res. 22:206-209)
#50 Walsh LP et al. Roundup inhibits steroidogenesis by disrupting steroidogenic acute regulatory (StAR) protein expression. Environ Health Perspect. 2000 Aug;108(8):769-76.
#51 ISU Weed Science Online - Are RR Weeds in Your Future II
#52 Glyphosate resistance is a reality that should scare some cotton growers into changing the way they do business
#53 More glyphosate resistant weeds
#54 Development and Characterization of a CP4 EPSPS-Based, Glyphosate-Tolerant Corn Event,G. R. Heck et al Crop Sci. 45:329-339 (2005).
#55 Molecular basis for the herbicide resistance of Roundup Ready crops, T. Funke et al, PNAS 2006 103:13010-13015
#56 Monsanto Company History
#57 USDA/APHIS Environmental Assessment - In response to Monsanto Petition 06-178-01p seeking a Determination of Non-regulated Status for + Roundup RReady2Yield Soybean MON 89788, OECD Unique Identifier MON-89788-1, U.S. Department of Agriculture Animal and Plant Health Inspection Service + Biotechnology Regulatory Services page 13 [.pdf]
#58 National Agriculture Statistics Service (2005) in Acreage eds. Johanns, M. & Wiyatt, S. D. 6 30, (U.S. Dept. of Agriculture, Washington, DC). +
#59 Impact of glyphosate-tolerant soybean and glufosinate-tolerant corn production on herbicide losses in surface runoff. Shipitalo MJ, Malone RW, Owens LB. J Environ Qual. 2008 37(2):401-8 PMID 18268303
#60 http://www.chem.purdue.edu/courses/chm333/Roundup%20Article.pdf [.pdf]
#61 California Product/Label Database
#62 Glyphosate Roadside Vegetation Management Herbicide Fact Sheet [.pdf]
#63 New Super Strain of Coca Plant Stuns Anti-Drug Officials. Jeremy McDermott. The Scotsman (Scotland) 27 August 2004
#64 USDA National Agricultural Library, accessed 1 Nov 2007
Feel better now? I don't have time to reproduce all the links, so check on the Wikipedia site if you need them. To the correspondent that asserted "if the facts were out there, people would do something about this" I can only respond that the facts have been out there and published extensively for many years now.
They have shown themselves woefully unable to compete with corporate marketeering.
And the disasterous consequences of the action of Monsanto that wil reverberate across decades? We, our children, and our grandchildren will hear the lament "Who could have known?"