OpenStax, a publishing initiative of Rice University, develops high-quality, peer-reviewed, openly licensed college textbooks that are absolutely free online and low cost in print.
The Open Textbook Library provides a growing catalog of free, peer-reviewed, and openly-licensed textbooks.
Open SUNY Textbooks is an open textbook publishing initiative established by State University of New York libraries and supported by SUNY Innovative Instruction Technology Grants and SUNY Geneseo.
Features open textbooks in children's literature, math, writing, and more.
The WikiBooks collection is managed by the Wikimedia Foundation and contains thousands of open textbooks ranging all subjects.
A non-commercial open textbook organization initiated at the University of California, Davis.
PHET
PHET Interactive Simulations project at the University of Colorado Boulder creates free interactive math and science simulations.
The OER Metafinder performs a simultaneous search across 19 different sources of open educational materials.
From a single point of access in OER Commons, you can search, browse, and evaluate resources in OER Commons' growing collection of over 50,000 high-quality OER.
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 72 different sources and contains 171,277 records.
The MERLOT system provides access to curated online learning and support materials and content creation tools, led by an international community of educators, learners and researchers.
Project Gutenberg offers over 57,000 free eBooks. Choose among free epub books, free kindle books, download them or read them online. You will find the world's great literature here, with focus on older works for which copyright has expired.
When searching OER repositories, adding the search term "video" or "media" to your discipline specific term helps focus on multimedia content resources/links. For example, putting "biology and video" in the search box. Below are a few repositories focusing on digital content.