USA.Gov for Science leads to authoritative science and applied science information compiled by U.S. Government agencies. Some of the sources require purchase.
The Animal Diversity Web is an online encyclopedia about animals sponsored by the University of Michigan. The web pages describe and illustrate specimens. College students prepared the entries for use under faculty supervision.
The Tree of Life Web Project is a phylogenetic or "evolutionary tree" explaining evolutionary sequence. The site has bibliographies, webliographies, photographs and videos with citations to authors.
Mammal Species of the World is a database of mammalian taxonomy. The site is currently under reconstruction but it still provides authoritative information in tables about the phylum.
Curious about the ecology of the West Coast? This web site prepared by the Department of Biological Sciences California State University at Stanislaus is an excellent starting point.
Science Daily Magazine is an “on-line newspaper” with introductory information written by respected journalists. The newspaper also has pictures and videos.