PhotoStuff

This seems to be an interesting tool for image annotation:

A variety of toolkits have been developed both commercially and in academia that provide the functionality to generate semantic metadata for the content on the Web. Currently, most existing toolkits provide an integrated environment to annotate only flat text on Web pages. However, we see the need to annotate additional media available on the Web as well. Given this motivation, we have developed PhotoStuff, a toolkit that provides users the ability to annotate regions of images with respect to an ontology and publish the automatically generated metadata to the Web

I found it via this WWW-2006 trip report.