November26
I was using Stumble Upon when I came across MacOSaiX, a free mosaic app for OS X.
It’s extremely easy to use, and pretty straight forward. First, choose an image you’d like to turn into a mosaic:

Next, choose the source of images you’d like to use. You can use DVD/CD/Book covers from Delicious Library, a folder on your computer, Flickr, Glyphs (which creates images out of fonts/colors/letters), Google Image Search, iPhoto, iTunes, or a QuickTime Movie.
Once you’re done with that, click Start Mosaic and MacOSaiX will work its magic. I turned off the animation of images to speed up the process, as it does take a while depending on how many images you’re using.
The mosaic pieces can be hexagonal tiles, puzzle pieces, or rectangular.
There are also tons of other options to choose from:
During or after the process, you can zoom in to see which photos make up the mosaic. Once you’re done, you can save as a JPG, PNG, or TIFF. Plenty of other options exist, such as Resolution (up to 600 DPI), height, width, and choosing a background.
MacOSaiX is extremely impressive with all the controls it provides, especially for a free program. I highly recommend this program, even if you’ve ever thought about doing a mosaic.
Here is a photo I wanted to turn into a mosaic.
Here is the photo as a mosaic using the photos I took from vacation (1,754 photos).
MacOSaiX homepage.