Open Textbooks have been released with an open license (usually a Creative Commons license) which allows them to be reused, remixed, and redistributes in courses for free.
Open Educational Resource Repositories contain more than just open textbooks. They also have other digital learning materials, covering all educational disciplines, such as:
Open CourseWare These are collections of materials submitted by faculty members at universities that are part of the OCW movement.
Finding Open Images: Some search sites and techniques to help you find openly licensed images.
In addition, Trible Library electronic resources can usually be linked to in your Scholar course shell to provide access to licensed material. Also, Librarians are experts in finding and evaluating resources. This includes Open Educational Resources (OER). Contact a reference librarian for more information.