"A network connecting Science with Conservation." This website provides links to natural heritage programs in all fifty states, most Canadian provinces, several Latin American countries, the NatureServe Explorer database, and much more.
North Carolina Natural Heritage Program
On this website, you can find GIS information pertinent to the study of endangered and rare plants, information about species, and access to the Natural Heritage Program's free online publications.
Center for Plant Conservation
This organization promotes conserving rare native plants of the United States. The National Collection of Endangered Plants (a collection of cuttings, seeds, and other plant materials) is maintained by the Center for Plant Conservation. Information about over 600 plants that compose this collection is available on this website.
Endangered Species Program
This is the site of the United States Government's Endangered Species Program. It includes information on organisms listed as endangered or threatened, including links to federal documents.
IUCN Red List of Threatened Species
IUCN, the World Conservation Union, produces this list of species (mostly birds and mammals) from around the world that are in danger of extinction.