Although many TUAW contests are limited to North American participants, here's a contest sponsored by a Belgian Mac development firm that is open to everybody!
Creaceed's Hydra 1.6 software is a Leopard-only solution for creating HDR (High Dynamic Range) photographs. If you're not familiar with HDR photography, it's a way of creating photographs that are closer to what the human eye actually sees (view Flickr gallery). To do this, you take two or more photos of the same scene; some are overexposed, some underexposed, some are just right.
For example, if you see a beautiful sunset with your own eyes, you can see details in both the sunset and the surrounding landscape. Since digital camera CCDs don't have the same dynamic range as your eyes, photos of the sunset usually show the landscape as being too dark. If you get the landscape "right", the sunset is washed out.
Hydra takes those photographs, aligns them, and then performs some algorithmic magic to create HDR images that are perfectly exposed across the entire photograph.
If you got a new digital camera for Christmas, give Hydra a try, and then enter your best HDR images into Creaceed's contest. Entry details can be found here -- good luck!