George Mason University Libraries has created the OER Metafinder, a robust search engine for discovering OER resources. The Mason OER Metafinder searches sixteen targets in real-time, returning the top several hundred or so relevant hits from each site. Because it is a real-time search, it takes a bit longer than searches of pre-indexed content; however, as compensation the results returned are absolutely up-to-the-minute for each search target. Additional results will trickle in as the search continues running and you begin examining your results.
As defined by UNESCO (2002 Forum on Open Courseware):
As defined by the William and Flora Hewlett Foundation: