The following resources contain open content, meaning that you can freely access and make use of the materials by providing a direct link. However, some resources may not allow for adaptations, meaning you can not download, modify, and repurpose the content. Check the licensing for each resource you use and when in doubt, use a direct link.
Openly Available Sources Integrated Search (OASIS) is a search tool that aims to make the discovery of open content easier. OASIS currently searches open content from 52 different sources and contains 155,375 records.
Searches 16 OER repositories in real-time, returning the top several hundred or so relevant hits from each site. Created by George Mason University.
Enter an ISBN number and find free online course materials related to a book.