ImageCropper for iOs is a drop-in image cropper for iOS (as seen in Photos app, UIImagePickerController)
I like this controle because it's so so simply and it shows images like iPhone Photos app (and I was looking for any sample!)
As always, you can download source source from https://bitbucket.org/hzaldivar/imagecroppersharp
I made a PhotoAlbumViewController based on this control and Escoz's PagedViewController. I'll upload source code soon!