Openly Available Sources Integrated Search (OASIS) From Milne Library at SUNY Geneseo (9/5/18): "We have gathered more than 155,000+ records from 52 different sources that have been carefully selected in collaboration with SUNY OER Services... we developed OASIS with the goal of making the discovery of open content easier. Some of the features of OASIS include the ability to limit search results by license, type, subject, source, and reviews available. Through OASIS, you can also suggest new sources to be added to the catalog and/or share items of interest through email."
The Mason OER Metafinder searches seventeen targets in real-time, instantly returning the top several hundred or so relevant hits from each site.
CC Search is a tool that allows openly licensed and public domain works to be discovered and used by everyone. Creative Commons, the nonprofit behind CC Search, is the maker of the CC licenses, used over 1.4 billion times to help creators share knowledge and creativity online." More at https://ccsearch.creativecommons.org/about