"American Memory provides free and open access through the Internet to written and spoken words, sound recordings, still and moving images, prints, maps, and sheet music that document the American experience. It is a digital record of American history and creativity."
One of the best places to start for all time periods of European history. Extensive collection of primary sources and links to other sites. Browse by broad era (prehistory/ancient, medieval/renaissance, modern) or by country.
The Internet History Sourcebooks are collections of public domain and copy-permitted historical texts. Topics include Ancient, Medieval and Modern histories. Also presents material grouped by subject: Africa, East Asia, Global, Indian, Islamic, Jewish, Lesbian/Gay, Science and Women's history.