Foldify is an upcoming iPad app that will let you create amazing 3D paper art right from your iPhone. Pick a form, paint it to your liking, AirPrint to suitable paper/card, fold it, and then the real fun begins.
But why am I telling you all this? Just watch the teaser video, smile, and wait for the launch.
(Or if you're really geeky, and want something to read in the meantime, check out this blog post on merowing by developer Krzysztof Zabłocki on how the line drawings were smoothed with cocos2d.)