I don't know that this app will ever make it onto my list of must-have camera apps for the iPhone, but it is good for some easy entertainment. The Lego Photo app turns any photo on your iPhone into Legos. While some photos are a little tough to see, tapping the Lego-ized version of any photo will change its Lego color scheme. Check out this photo that I changed; it's the same shot I used to compare the cameras on the Droid and iPhone. Can you see the bridge?
The app is free, and it's fun to play around with. Upload photos you currently have on your phone, or take a shot through the application. Then save photos to your phone's photo album simply by tapping the Save button.