Ecology

Earth 911: Lots of "Green" information

DES: Deptartment of Environment Services, New Hampshire; Waste Management

ECD: Energy Citations Database.  Provides access to historical and current research (1948 to the present) from the Department of Energy (DOE)

EPA: Environmental Protection Agency

Fuel Economy.gov

National Service Center for Environmental Publications (Environmental Protection Agency)
Full-text of nearly 25,000 documents in all areas of the environmental sciences. Keyword options.

Union of Concerned Scientists
A plethora of information on all types of environmental concerns, from global warming to food to security, etc.