In iOS 5, the Photos app allows you to edit and crop images directly on your iPad and iPhone device, and you are able to save them to the photo library.
How to Crop Photos on iPad running iOS 5
* From the device's Home Screen, tap Photos app and navigate to the image that you want to crop.
* Choose the photo and tap "Edit" button.
* In the bottom right corner of the screen, there is a crop icon . Tap the icon.
* Before begin cropping, tap the "Constrain" button to select the image size.
* Now you can pinch with two fingers to zoom in/out, or move the entire image freely by tapping and dragging it with one finger.
* Then tap the Crop > Save button to save the edits.