Heads up: Creative Commons has officially launched CC Search, a search engine that indexes over 300 million images from 19 image collections, "including cultural works from museums (the Metropolitan Museum of Art, Cleveland Museum of Art), graphic designs and art works (Behance, DeviantArt), photos from Flickr, and an initial set of CC0 3D designs from Thingiverse." All of the indexed images are in the public domain and released under Creative Commons licenses--meaning the images are generally free to use in a non-commercial setting.
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