Faunmap - An electronic database for the late Quaternary distribution of mammal species in the United States. - http://www.museum.state.il.us/research/faunmap/
North American Fossil Mammal Systematics Database - Consists of phylogenies, taxonomic histories, age-ranges, and body mass estimates for genera and species of Cretaceous and Cenozoic North American fossil mammals. By John Alroy - http://www.nceas.ucsb.edu/~alroy/nafmsd.html
Tree of Life Project: Mammalia - Hierarchial Phylogeny of Mammals both living and extinct. JAVA applets. Searchable. - http://tolweb.org/tree/eukaryotes/animals/chordata/mammalia/mammalia.html