Ditto (www.ditto.com) is a visual search engine that predates Google's visual search engine (images.google.com).
History
Ditto went live with their visual search engine on August 2, 1999. They initially served image results via their website, www.ditto.com, and one partner site, Snap (then a joint venture between NBC and CNet).
Milestones
Ditto helped to establish current copyright law regarding the use of copyrighted images in image search engines in 2000. In the case of Leslie A. Kelly v. Ditto.com, California judge Gary A. Taylor ruled that the use of the images amounted to fair use, because Ditto offered ways for web site operators to prevent their materials from being indexed by web spiders. This ruling was upheld upon appeal.
As an aside, I have worked at Ditto for the past several years.