OpenStax from Rice University offers free, online educational materials and textbooks, some of which can be printed at an affordable price.

The Open Textbook Library at the University of Minnesota offers a catalog of open, peer-reviewed textbooks that can be downloaded for free.

A pilot open textbook publishing initiative established by State University of New York that engages faculty as authors and peer-reviewers and libraries as publishing service and infrastructure.

BCcampus has curated a collection of open textbooks that align with the top 40 highest enrolled first and second year post-secondary subject areas in British Columbia. Many books have been reviewed by faculty and include ancillary resources. Particular strengths include

In addition to other open educational content, Saylor Academy offers over 100 open textbooks under a variety of Creative Commons licenses.

Open textbooks that have been approved by the American Institute of Mathematics.

InTech is the publisher of one of the largest open access collection of books in the fields of Science, Technology and Medicine.

An index of online textbooks in MIT OpenCourseWare, including open-licensed electronic versions of print books, self-published online books, or course notes which are so thorough that they serve as an alternative to a conventional textbook.

The College Open Textbooks Collaborative maintains a catalog of open and/or affordable textbooks appropriate for lower division university classes. Some resources have been peer-reviewed.