CameraBag CameraBag applies 11 different effects, inlcuding a number of "toy camera" looks. It can make any boring photo look interesting.

Adobe Photoshop Express It's free, and gives you all the tools - like cropping - that should be part of the built-in iPhone tools.

TiltShift Generator - Fake Miniature Make any scene - especially ones from higher floors of buildings - look like a miniature diorama. Very cool effect.

PanoLab Stitch multiple photos together to make panoramas. A little clunky, but still fun.

Photo Radar This map is more about helping you take good pictures -later- than it is about taking pictures with your phone. The app geotags a phone snapshot, helping you find your way back later when you have your higher rez camera.

GorillaCam This is simply a great replacement for the iPhone's native camera app, and it's free. Touch-anywhere shutter, zoom, time lapse capture, bubble level and more!