The Animal Diversity Web is a collection of pictures and information about animals.  The information is arranged by taxonomic groups, and includes such topics as distribution, natural history, conservation, economic importance, as well as pictures and sound, if available.  The site is also searchable by animal name.
 

Dinosauria On-Line :  http://www.dinosauria.com

This site presents information about the various aspects of the lives and habitats of dinosaurs.  It also provides a dinosaur names dictionary, pronunciation guide, and maps of the ancient earth. 
 

EarthTrends :  http://earthtrends.wri.org

Provided by the World Resources Institute, EarthTrends is an environmental information portal offering searchable databases, data tables, country profiles, maps, and feature articles in ten topical sections. 
 

eNature.com :  http://www.enature.com

Contains information on over 4,000 species of North American animals and plants.  Content is provided by Audubon Field Guide books. 
 

Envirofacts :  http://www.epa.gov/enviro/index_java.html

From the U.S. Environmental Protection Agency, Envirofacts provides access to over eleven EPA databases.  Information provided includes hazardous waste locations, pollution, and other regulatory information. 
 

ITIS : Integrated Taxonomic Information System :  http://www.itis.usda.gov

This database provides authoritative taxonomic information on animals, plants, and microbes found world-wide.  Offers keyword searching by common name or scientific name.