OpenStaxCollege Free course materials for 25 common introductory classes. The textbooks are open to classes anywhere. OpenStax is partnering with OER Commons to provide online community hubs where instructors can freely share and modify syllabuses, homework, study guides and other open-copyright course materials.
OER Commons is a digital public library that offers tools for collaboration, sharing and remixing openly licensed course materials. It features tools for evaluation, quality review and improvement of high-quality resources.
Platform for shared educational texts -- view and share educational material made of small knowledge chunks called modules that can be organized as courses, books, or reports. Anyone may view or contribute.
WikiBooks An online wiki-based collection of over two thousand open-content textbooks. Fully editable, published under the Creative Commons Attribution-Share Alike License.