Photoshop has finally omes to the iPhone.... kinda. Note that the app you search for in the store (if you don't just click on this link) is 'photoshop.com', not photoshop, and that's because it's fairly closely tied with the online service at photoshop.com. It's also missing some nice-to-have features that other apps (such as photogene, which is, as an aside, on sale this weekend) have.
Still it's free and have some good features to have without being over complicated. I'm looking forward to trying it out and seeing how it is.
As an aside, here's a test image in my Photoshop.com account. It's basically a bit of a vibrancy pump, a bit of soft focus filter, and a tweak here and there: