Large, user-generated databases of online materials are often a good place to start your search. These databases allow you to browse resources by subject as well as search for specific materials.
However, with the number of materials uploaded to these sites, it can be overwhelming. Pay attention to the filters you can use, specifically: format/resource type and level (example: lower division undergraduate).
OASIS (Openly Available Sources Integrated Search). We have gathered more than 155,000+ records from 52 different sources that have been carefully selected in collaboration with SUNY OER Services.
Many colleges and universities have developed repositories for open materials. The following are some of the largest in the nation.