British Columbia (BC) Campus OpenED Textbooks
A Canadian OER organization that features a variety of subjects. Search by subject or course.
Offers fully digital textbooks, interactive tutorials, and homework assignments across 17 subject areas.
MIT Open Courseware: Textbooks
Textbooks listed are components of courses, most of which are STEM-based.
Choose subject under the heading "Online Textbooks by Department," choose title, and either download each chapter needed or download all course materials by navigating to "Download Course Materials" and clicking the "Start Download" button.
Features a variety of disciplines. To View: Refine list by "Subject Area," select title, and click "View Resource".
OERTX Texas Repository Textbooks
Search by subject area.
A non-profit initiative through Rice University that offers free college textbooks online and the same in print for low cost. Caveat: not as much content in the humanities.
Currently offers over 1600 open textbooks in 12 subject areas.
Computer Science and Mathematics textbooks.
Computer Science textbooks.
Focused on the science disciplines.
Psychology textbooks
Simple list of freely available math books compiled by George Cain at Georgia Institute of Technology.
Humanities and social science textbooks
Open Textbook Initiative, American Institute of Mathematics
Mathematics textbooks
Most textbooks are focused on mathematics and writing.
Textbooks for Writing and Composition Classes
WAC Clearinghouse Other Open-Access Book Series in Writing Series
This resource links to other publishers of scholarly open-access textbooks within the field of writing studies.