Red List of Threatened Species - biannual assessment of the status of species and subspecies, highlighting taxa threatened with extinction. International Union for Conservation of Nature.
World Conservation Union (IUCN) - works to conserve the integrity and diversity of nature and to ensure that any use of natural resources is equitable and ecologically sustainable.
NatureServe - source for information about rare and endangered species and threatened ecosystems.
Endangered Species [EE-Link] - compendium of information about endangered species that can be found on the Internet including factsheets, searchable databases, images, policy, and legislation.