I have wasted so much time playing with AndreaMosaic! You tell it where your digital photos are on your computer and give it a picture, and it makes a photo mosaic of the picture! The software is a free download and includes instructions and many settings to change the outcome.
Most of the mosaics I have made look better small. When you make them bigger, you can see the individual photos better, but the overall picture fades. Click on the images above to see more detail.
One reason I like this program is that it gives me something to do with all the digital photo slush on our computer. I toss all the extra photos into another folder and the program uses them along with all of our best. This serves a dual purpose: more mosaic fodder and a backup in case I decide I want something back later.
You can see some amazing mosaics and download the software at the website.