Bookboon.com contains free eBooks and textbooks that can be downloaded as a pdf, no registration needed. These books cannot be altered, but can be freely printed, shared, or embedded in non-commercial ways. They are intended only for individuals, colleges, and schools.

The Open Textbook Library provides a growing catalog of free, peer-reviewed, and openly-licensed textbooks. The Open Textbook Library is supported by the Center for Open Education and the Open Textbook Network.

MIT OpenCourseWare (OCW) is a web-based publication of virtually all MIT course content. OCW is open and available to the world and is a permanent MIT activity.

Open Learn is an initiative of The Open University, UK. It provides supplemental materials for educators, including articles, podcasts, videos, games, and much more. In addition, it offers more than 700 free online classes.