The following repositories have a mix of overlapping and unique content.
American Institute of Mathematics
Open textbooks evaluated and approved by the AIM editorial board.
An extensive collection of texts, including harder-to-find subjects like business, philosophy and media/design.
Lumen Learning creates digital course materials to replace expensive textbooks. Courses are divided into modules for easy customization and may include assessment tools, instructor resources, or multimedia content.
Based at Rice University, the OpenStax mission is to provide students with cost savings at scale. Content is formatted like a traditional textbook and focuses on high enrollment, introductory courses in math and science. Print versions are also available for purchase.
Open SUNY Textbooks
Textbooks authored and peer-reviewed by faculty in the State University of New York (SUNY) system. This collection is small but growing and features textbooks for a wider variety of courses than OpenStax.
Open Textbook Library
A clearinghouse of open textbooks that are either in use at multiple colleges and universities or affiliated with an academic institution, scholarly society, or professional organization.
Saylor Academy Open Textbooks
A curated collection of 100+ textbooks in a wide range of disciplines. Books are used to support Saylor's self-paced open courses.
OER undergo varying levels of editorial and peer review. The tools below can help you evaluate the quality and suitability of a resource.
Open Textbook Network Review Criteria
A rubric used by OTN member institutions that considers comprehensiveness, accuracy, clarity, organization, etc. It is less detailed and more flexible than the ACHIEVE.org rubric.