I use Infinicam, but just for post-processing pictures taken with another app. I've gotten to like it a lot. There's kind of a long set-up curve, in that most of the randomly chosen effects don't look so great with a given picture. But over time, as you discover settings that you like, you can save them as favorites, and after a while you've got a nicely customized app that sometimes -- sometimes -- produces amazing results.
Lo-Mob is a lot of fun, too. And I second another commenter's recommendation of PictureShow.