According to the Hewlett Foundation, open educational resources (OERs) "are teaching, learning and research materials in any medium--digital or otherwise--that reside in the public domain or have been released under an open license that permits no-cost access, use, adaptation and redistribution by others with no or limited restrictions."
Austin Community College's Library Services provides a very thorough guide on Open Educational Resources at the link below.
From the Texas Higher Education Coordinating Board, OERTX Repository is a public digital library of open educational resources for higher education. Search collections or create and collaborate to improve instruction.
Following are "some examples of OER material: full university courses; interactive mini-lessons and simulations; adaptations of existing open work; electronic textbooks; and elementary school and high school (k-12) lesson plans, worksheets, and activities."
A list of currently available Open SUNY Textbooks, an open textbook publishing initiative established by State University of New York libraries and supported by SUNY Innovative Instruction Technology Grants and SUNY Geneseo.
panOpen is a platform that enables adoption of Open Educational Resources, combining established and authoritative OER texts with enhancements to add to the ease of use of the learning materials. There is no cost to the faculty for adoption, but an affordable access cost for the student, either as a low cost per chapter or the entire text.