The links below lead to major OER hubs that provide open textbooks along with a variety of other teaching and learning resources.
Largest catalogue of open sources textbooks. Also is a good place to find free books about math, science and computers.
Athabasca University Press - free pdf and low cost print version of mainly Canadian books.
Search the BCcampus open collection
Collection of open textbooks and other open resources
A partnership of academic & research institutions, offering a collection of millions of titles digitized from libraries around the world.
Non-commercial open textbook organization initiated at the University of California, Davis. Students, faculty, and outside experts work together to build OER. Currently covers 12 widely used college-level disciplines from chemistry to humanities with over 68,500 pages.
The MERLOT system provides access to curated free and open online teaching and learning support materials and content creation tools, used by an international community of educators, learners and researchers.
Formerly known as "Open SUNY Textbooks." Contains the open textbooks authored and peer-reviewed by SUNY (State University of New York) faculty and staff.
Contains freely accessible academic books, mainly in the humanities and social sciences.
Worldwide learning network of shared teaching and learning materials.
Peer reviewed post secondary textbooks
One of the largest repositories of open textbooks.
Provides an index of over 3200 books published across 110 Pressbooks networks.
Wikimedia's community for creating and sharing educational textbooks.
Based on library guide "Open Education Resources (OERs)" by TRU Libraries which is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
TRU Libraries guide is based on a work at http://open.bccampus.ca/bcoer-librarians/bcoer-guides/.