Open Educational Resources (OER) are freely accessible, openly licensed documents and media that are useful for teaching, learning, skills building and assessment of learning. They range from individual modules or objects to entire courses, textbooks, demonstrations, etc. An Open Textbook is a textbook licensed under an open copyright license and made available online to be freely used by students, teachers and members of the public.
Essentially these are freely available teaching tools that can be modified and used to enhance or replace traditional textbooks.
Meta Search Engines for OER
JSTOR has launched an Open Access (OA) ebook program with the goal of making this type of scholarship easy for researchers to discover and use, and to preserve this content for future generations of scholars.