Chemfinder - chemical structure and toxicology
Chemical Awareness
Green Chemistry network - coordinated by the UK Royal Society of Chemistry
Greenpeace Chemical Kitchen
PAN Pesticide Database - largest and most comprehensive online collection of pesticide data in the world
Toxicology - a list of sites providing useful info.
US Environmental Defense Fund Chemical Scorecard - chemicals and pollution + emissions maps
US EPA Chemical Hazard Data Availability - report & associated information re lack of data available about many chemicals