The Copyright for Ernst Häckels illustrated book Kunstformen der Natur (Artforms of Nature) from 1904 has expired and is now available for everyone. Check out his fascinating work here.

Wikipedia:

Ernst Heinrich Philipp August Haeckel (February 16, 1834 – August 9, 1919), also written von Haeckel, was an eminent German biologist, naturalist, philosopher, physician, professor and artist who discovered, described and named thousands of new species, mapped a genealogical tree relating all life forms, and coined many terms in biology, including phylum, phylogeny, ecology and the kingdom Protista.

via [Swen's Weblog]