A list of open textbooks in various subdisciplines of Mathematics approved by the AIM editorial board.
Open Textbooks on Aviation from the Federal Aviation Administration (US).
A curated collection of open textbooks, many reviewed by British Columbia faculty.
Bloomsbury, a well-respected and long-time UK publisher, has released some of their academic titles for open access/open education.
This effort, funded by the Hewlett Foundation, seeks to drive adoption of open textbooks. Many of the books shared on this resources are reviewed.
Free medical textbooks.
High-level texts hosted or created by the University of Georgia.
Lyryx offers high-quality open textbooks in the fields of accounting, mathematics, and economics. They also have optional added (paid) resources such as homework and quizzes to accompany the open textbooks.
Contains peer reviewed, quality open textbooks with interactive components. There are some amazing textbooks available here, with more in production.
Hundreds of complete, open college-level textbooks collected by the University of Minnesota.
Find the full text of classics and public domain works from the first massive ebook creating organization in existence. Nothing fancy here, just files with the full text.
A project of the Wikimedia Foundation, this collection of group written textbooks in a variety of sources follows rules similar to Wikipedia.