The University of Texas/Austin's map colletion--world maps, maps of continents and regions, historical maps, and links to other map sites are available. Most maps are public domain . See their Library Web Material Usage Statement for details regarding any exceptions. Provided by the University of Texas.
Digital collections provided by the good people at Archives Canada. Wouldn't it be great if all national archives digitised their collections and made them available for public domain?
An excellent collection of public domain ebooks run out of the University of Adelaide, focussing on literature, philosophy, science and the queen of all subjects, History. She deserves a capital.