Information about many animals by name, species, etc.
Animal Diversity Web - an online database of animal natural history, distribution, classification, and conservation biology at the University of Michigan
Animal Corner - Gives description, habitat, diet, behavior, reproduction, and conservation status. British site.
Birds of North America - Alphabetical list of birds found in North America, by both common name and scientific name. From the Cornell Lab of Ornithology and the American Ornithologists' Union. Only part of the information is viewable. A subscription is required for seeing all the content.
Animal Omnibus - Originally began as part of the website of the City of Birmingham Zoo in Birmingham, Alabama. Site is now independent and separate from the zoo. They do not actually host any content, but provide a directory of animal websites, by the type or species of animal.