Big Ten Open Books is a collaboration between the university presses and libraries of the Big Ten Academic Alliance. The first collection is on the subject of Gender and Sexuality studies. Participating presses are Indiana University Press, Michigan State University Press, Northwestern University Press, Purdue University Press, University of Michigan Press, and University of Wisconsin Press.

This collection has established a model for unified, open-access publishing of scholarly monographs. It creates open content, on open infrastructure, using open distribution models - to envision a robust programmatic future for open monograph publishing. This work is aligned with the Big Ten Academic Alliance’s development of the BIG Collection's ambition of uniting the collections of the libraries of the Big Ten Academic Alliance, and is supported by The Andrew W. Mellon Foundation's Public Knowledge program.

Millions of books digitized by a variety of major research institutions. See this post for more information about public domain items available to all via HathiTrust.

The Internet Archive, a 501(c)(3) non-profit, is building a digital library of Internet sites and other cultural artifacts in digital form with a mission to provide universal access to all knowledge. The archive contains tens of millions of books and texts, audio recordings, videos, images, and software programs, and 625 billion web pages.

An initiative of the Internet Archive, Open Library is a universal catalog with the goal to create a web page for every book ever published. The catalog provides links to the Internet Archive’s collections with over 1.7 million public domain books available for download, and hundreds of thousands of ebooks that can be borrowed via controlled digital lending. Some digitized books are available only to the print disabled. See information about creating an account and borrowing from the Open Library and FAQs for further details.

Project Gutenberg is a library of over 60,000 eBooks, mostly items in the public domain. Choose among free epub and Kindle eBooks, download them or read them online. An open access crowdsourced project.