DPLA connects people to the riches held within America's libraries, archives, museums, and other cultural institutions. All of the materials within DPLA are free and immediately available in digital format.
HathiTrust
The Hathi Trust began in 2008 as a collaboration of 13 universities to preserve the cultural record. Focusing on providing access to digitized book and journal collections, there are now over 10 million digitized items with over 2,000,000 freely accessible.
Directory of Open Access Books
Find peer reviewed books from academic publishers.