Although pretty basic, I'm finding the onboard processing app from TheBestCamera.com gives me great results without having to rely on a computer.
Disclaimer... cropping was done in PS, but all image/color processing was done on the phone with the app's filters and white boarder option.
Pet pic taken with older 3G, the franken 111 with a 3GS. Lighting was mixed with no effort made to control it.
Best $2.99 I ever spent on software.
http://www.thebestcamera.com/app.html