Many of the photos we take have perspective problems, but there are not too many utilities for iOS that deal with it. The iPhone has a fairly wide-angle lens, and as a result, pictures of city buildings, landscapes with lots of trees, almost anything with vertical lines can need some perspective correction.
Perspective Correct (US$1.99) is a new app that deals with just this problem. You import a photo and then by swiping across the screen you can change vertical or horizontal distortion. After that's corrected, you'll need to crop the photo and the app includes a built-in cropping tool. There is also a tool to make a white or black background around the image.
You can also get perspective problems with indoor photography and even taking portraits where distortion could result in a big nose or a swelled forehead.
I tested the app and it worked as intended. I'd like to see an undo command, because once you make the changes, you are stuck. The app is not universal, and is clearly intended for the iPhone, but I think a full-resolution version for the iPad should be offered. The app requires iOS 5 or greater and is optimized for the iPhone 5. Perspective Correct works well and is a welcome addition to my folder of photo editors.