EPA Office of Prevention, Pesticides and Toxic Substances
Evaluates pesticides and other chemicals to safeguard people, including children and other vulnerable members of the population.
http://www.epa.gov/opptsmnt/

EPA Toxics Release Inventory (TRI)
The TRI describes releases of toxic chemicals to the environment from manufacturing facilities. The database is searchable by zip code.
http://www.epa.gov/epahome/r2k.htm

The Right-to-Know Network
A service provided by OMB Watch, provides free access to numerous databases, text files, and conferences on the environment, housing and sustainable development. The site provides databases to identify chemical releases in your neighborhood, toxic waste and industry compliance. Databases include Superfund Sites, chemical accidents and spills, EPA regulated facilities, permit compliance, and civil cases filed by the Justice Department for the EPA.
http://www.rtk.net

USGS - National Water Quality Assessment Program
This site provides information and data on pesticide usage in the USA by county as well as concentrations occurring in surface and groundwater, statistical summaries, and analytical strategies.
http://water.usgs.gov/nawqa/

Your Drinking Water: Pesticides
An article about the levels of pesticides in drinking water and their associated risks.
http://www.ces.uga.edu/pubcd/C819-6W.html

National Library of Medicine, Toxicology and Environmental Health Program website
This web site contains databases regarding environmental health and toxicology. One database allows you to search by chemical name or structure.
http://sis.nlm.nih.gov

Environmental Protection Agency, Office of Air and Radiation
Lots of information on air pollution, air toxics, urban air quality and more.
http://www.epa.gov/air

Extension Toxicology Network (Extoxnet)
A multi-university effort, this resource contains an abundance of both general information on toxicology, pesticides, and environmental health as well as specific information such as health effects of pesticides, current issues in toxicology, and environmental fates and consequences of toxins and much more.
http://ace.orst.edu/info/extoxnet/

National Institute for Environmental Health Sciences
This site provides a wealth of information on environmental effects of pesticides, articles on environmental health topics, fact sheets on the toxicity of chemicals to humans, and details of research programs, as well as links to other sources of information.
http://www.niehs.nih.gov/

National Toxicology Program
Find information on chemical testing, chemical safety, and publications from the national program charged with determining chemical toxicities.
http://ntp-server.niehs.nih.gov/