OpenStax is a nonprofit educational initiative based at Rice University, OpenStax is one of the most popular OER repositories in use today, The textbook projects are developed and peer-reviewed by educators to ensure they are readable and accurate, meet the scope and sequence requirements of each course.
The Open Textbook Library provides an easy-to-use interface for locating and evaluating OER. "The textbooks have been funded, published, and licensed to be freely used, adapted, and distributed. These books have been reviewed by faculty from a variety of colleges and universities to assess their quality. These books can be downloaded for no cost, or printed at low cost."
The State of Oregon has funded OER creation and adoption by the community colleges and universities. Browse or keyword what has been adopted by courses." Not all of them are OER, some are open access titles or ones they got via their library's purchases.