Searches 7 sites, including: http://www.freephotosbank.com/, http://openphoto.net/, http://pdphoto.org/, http://www.freedigitalphotos.net/, http://flickr.com/creativecommons/

My Google custom image search engine.

A search engine for Creative Commons images.

PicsLikeThat is a prototype image search system combining a keyword search with a visual similarity search and semi-automatically learned inter-image relationships.