easy to setup, good results!
reading an article in c't (german it-mag), I gave GIFT a chance the other day. while I'm quite novice according linux, it was quite easy to install.
I fed the picture-database with about 1000 photographs of outdoour-advertisment-billboards, and, to my own surprise, the content-based queries did work to an enormous extent! the only down is the time it takes to create the picture-idnex/db - for this about 1000 pictures (very high resolution!) my p2-linuxbox needed about 6 hours...
but anyway, if you are interested in content-based search-engines for pictures, GIFT is definitley a MUST!
An open, cross-platform journaling program.
A scientific plotting package.