"OER are teaching, learning, and research resources that reside in the public domain or have been released under an intellectual property license that permits their free use and re-purposing by others. Open educational resources include full courses, course materials, modules, textbooks, streaming videos, tests, software, and any other tools, materials, or techniques used to support access to knowledge." 
The Open Education movement is built around the 5Rs of Open 
OER are educational materials that are specifically designed by their creator/s to be openly available, and are often licensed to be re-used, re-mixed, and re-distributed. Open is not just about low cost (though that is an important benefit of using OER) but about the ability to take what others have created, customize it for your specific educational needs, and then share your creation with others.
OER come in a variety of forms:
The open resource movement has been around for a while, starting with static learning objects (about 2000), and transitioning to OER that allowed for revision and reuse. It is the ever increasing cost of textbooks and materials for students that is now pushing the OER movement forward. Textbooks and learning materials cost students approximately $1,200 per year. According to the Chronicle of Higher Education, 7 in 10 students didn't purchase a textbook because it was too expensive. Through OER the cost of student materials can be drastically reduced. OER also give instructors the ability to customize the materials, creating the "perfect" textbook instead of being bound to traditional print resources.
The first step is finding OER, and that is what this guide is designed to do, so check out
If you have questions about open licensing (Creative Commons Licensing), you can find out more in the guides.ou.edu/CreativeCommons site.
SPECIAL NOTE: This page is specifically designed to introduce OER to the university community, but don't forget that there are electronic resources available to you through the University Libraries. OU Libraries has licensed journals, databases, primary content, and an increasing number of ebooks. These resources are restricted to University faculty, staff and students (you have to have an OU log-in to access), they do not allow for customization and re-use in the same way as OER. Though these are not "open", they are resources that you can make available at not cost for your students.