This document provides an introduction to open educational resources (OER) which include materials like videos, podcasts, course materials, and textbooks that are available online for free use without royalty or licensing fees. It lists two major sources of open textbooks, OpenStax and Flat World Knowledge, and provides additional resources for finding open textbooks including links to lists on Openculture.com, the OER Consortium site, and the Student PIRGs catalog. The document aims to define and explain OERs while pointing the reader to sources to find open educational materials and textbooks.