We've seen a lot of photo editors in these parts, but Wrapcam takes a different approach to editing and enhancing photos. Even better, this app is free until approximately noon PDT tomorrow.
Besides all the usual filters for framing, color saturation and so on, this app lets you take your photo and wrap it as if it were a piece of paper. There are several presets for this, and you can modify most filters by swiping on your device screen. There are nice page-curl filters, scroll effects and dozens more.
I tried the app on some photos already on my phone, and liked the results. You can also bring the live camera up from within the app. There is an undo command, and a compare command that lets you see your original and quickly switch to the filtered versions. Any image can be shared via the more popular social networks or emailed.
There is a very nice Quicksharp filter that is effective, as well as filters that simulate rain, embossing, oil paints and crayon. There is built in help, and links to video tutorials.
Wrapcam is a very nice app, and I would suggest you grab it while it is free. After that, it is a very reasonable US$0.99. I like it enough to add it to my permanent folder of photo editors. There are separate versions for iPhone and iPad.
Wrapcam is optimized for the iPhone 5, and requires iOS 4.3 or greater.