I've been playing around a little with the camera apps on my new 'mobile device' - I certainly prefer to take photos with my DSLR, but it's nice to have a lightweight eight megapixel camera on me at all times. Since I bought an Android, not an iPhone, I'm missing out on the popular "hipstamatic" app - but I've found a couple Android-friendly apps that are fun to play with. Thus far, my favorites are retro camera and paper camera.
Taken with the retro camera app, pinhole camera setting.
Taken with the paper camera app, sketch up setting.