"Animal Diversity Web (ADW) is an online database of animal natural history, distribution, classification, and conservation biology at the University of Michigan." It includes a comprehensive, searchable encyclopedia, a virtual museum, and a parallel site
The FieldGuides to more than 5,500 species of animals and plants are the core content here at eNature. The species are searchable by keyword, color, size, region and even zip code!
The kids' section of the American Museum of National History (for elementary and middle-school kids) covers all kinds of "ology" including anthropology, marine biology, palenotology and this zoology section.
Surfnetkids.com recommends five websites about zoology.