I love Vignette, and Camera 360. You need the pro version of these to get full-res.
Camera 360 has really cool film effects and color effects, with some worthless ghost effects and scene effects.
Vignette lets you take pictures with effect, but then edit them with different effects after you've taken it. More usfull as a post-production app than a camera app, IMHO.
Photoshop Mobile lets you edit photos as well, but VERY basic (contrast, brightness, saturation, etc.) Does not live up to the photoshop name, but try in anyways.