Discover Life
Information about taxonomy, natural history, distribution, abundance, and ecology of many different groups of living things. Discover Life has information on over a million species.
http://www.discoverlife.org/

All Species Toolkit
Provides search access to several different taxonomic databases. Search by genus, species, or common name.
http://www.speciestoolkit.org/

BiologyBase
Covering the broad spectrum of species taxon, BiologyBase aims to be a one stop shop for information about the diverse range of flora and fauna that exist on our planet today.
http://www.biologybase.com/