Open Education Resources are defined as free materials used for teaching and learning. In higher education, these include courseware, textbooks, digital sources, open access journals, and government documents.
Open textbook sites are committed to providing quality, affordable (often free), electronic textbooks and advocating for their creation and use by faculty. Adopting an open textbook for your course could save students hundreds of dollars and allow them the convenience of always having their textbook at their fingertips. Some sites offer the additional flexibility of adding to and editing these textbooks, meaning you could customize the content to meet your course objectives.
Many universities have followed MIT's lead and model for open courseware (OCW). OCW Course materials are freely accessible but no certificates or degrees are granted by the institution. The intent is to share knowledge and resources with all who interested in learning.
More information about Open Courseware is available at the Open Courseware Consortium site.