Bookboon.com contains free eBooks and textbooks that can be downloaded as a pdf, no registration needed.

College Open Textbooks (COT) focuses on textbooks for lower division classes. COT is not a repository of open textbooks; our listings point to textbooks on many repositories.

The Global Text Project is a joint initiative between the Terry College of Business at the University of Georgia and The Daniels College of Business of the University of Denver to publish eBooks that can be accessed by all, especially the developing world.

InTech publishes more than 2,300 open textbooks and 6 journals in a variety of subjects that fall under the heading of science, technology, and medicine.

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.

Hippocampus offers educators a wide variety of multimedia content online, including videos, animations, and simulations. An additional feature offers educators the ability to create "playlists" for their students, which correlate specifically to their particular instruction material.

The AAPT ComPADRE Digital Library is a network of free online resource collections supporting faculty, students, and teachers in Physics and Astronomy Education.

Founded in 2002 by Nobel Laureate Carl Wieman, the PhET Interactive Simulations project at the University of Colorado Boulder creates free interactive math and science simulations. PhET sims are based on extensive education research and engage students through an intuitive, game-like environment where students learn through exploration and discovery.

Open source textbooks that are written by professional content developers who are experts in their fields and undergo a rigorous peer review process. All textbooks meet standard scope and sequence requirements.

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.

MERLOT is a curated collection of free and open online teaching, learning, and faculty development services contributed and used by an international education community. The MERLOT Collection is made up of over 40,000 materials in 19 different material type categories.

OER Commons helps educators, students, and lifelong learners avoid time-consuming searches and find exactly the right materials. With a single point of access from which they can search, browse, and evaluate resources in OER Commons’ growing collection of over 50,000 high-quality OER everyone can more efficiently find what they need.