Angiosperm Phylogeny: Phylogenetic trees, technical descriptions of all orders and families, references, and links. By Peter Stevens of the Missouri Botanical Garden.
Angiosperms Image Gallery: Extensive collection, organized by family.
Flowering Plant Gateway: Various paths for exploration or comparison of four major flowering plant classification systems (Cronquist, Takhtajan, Thorne and the Angiosperm Phylogeny Group system). From Texas A&M University.
OSU Seed Biology Program - SeedID Index: Photographs of the seeds of selected plants.
The Families of Flowering Plants: A taxonomical database with descriptions and illustrations of each family, and an interactive key to families.