Been playing with the MacOSaiX photo mosaic software recently. For those that don’t know what photo mosaics are (where have you been living?), they are images made up from lots of smaller images. You provide the software an image that you’d like to convert to a photo mosaic, and a collection of photos to make the small tiles. MacOSaiX is slightly different from others here in that it also allows you to specify Google Images search terms as sources for the tile images.
An article at Engadget was what pointed me to this software, and it also has a recommendation for Windows users (Andrea Mosaic). So far it has not done badly, though I am only trying the stable version. The newer version is for 10.3 (though it says it might run on 10.2 machines), so I haven’t tried that yet.
The example below shows the original, the pure mosaic and the mosaic with an almost transparent overlay of the original image (this was added in Photoshop afterwards). These were done using images from my entire iPhoto library (click on each for a slightly larger version).