Species accounts 1-787 (1969-2005) of Mammalian Species, full-text, published by the American Society of Mammalogists. Each account includes a complete, concise description of a particular species, including anatomy, behavior, systematics and ecology.
http://www.science.smith.edu/departments/Biology/VHAYSSEN/msiMammal Species of the World, 3rd edition (MSW3) is a database of mammalian taxonomy. The names are organized in a hierarchy that includes Order, Suborder, Family, Subfamily, Genus, Species and Subspecies.
http://www.bucknell.edu/msw3/