Over 16 million freely usable media files. Like Wikipedia, anyone can contribute to the collection. Copyright and licensing information is provided for every image.
Click the camera icon in the search box and search by the image you have in hand (either by URL or by dragging in). Like TinEye, it finds other places online where the image has been posted.
(Searches through citations and subject indexing)
A large collections with artworks, artifacts, books, videos and sounds from across Europe. Has filters for Open Licenses.
Flickr is a photo-sharing Web site. Many users of the site choose to offer their work under a Creative Commons license, allowing greater flexibility for use than standard copyright.
Collection of photographs that are free of copyright restrictions from dozens of cultural institutions around the world, including the Smithsonian, several U.S. museums, several state archive, NARA, and New York Public Library. Be aware that this is a separate Flickr stream from the main institutional Flickr sites, which often contain copyrighted images. Also note that the Internet Archive Book Images collection is here.