The iPhone lacks any photo editing or manipulation of any kind. All you can do is take 'em, look at 'em, and save 'em. That's where Photogene comes in.
Before uploading those snapshots to your computer, Photogene allows you to crop them, add frames or humorous speech balloons, rotate them, or even use a histogram to adjust brightness and contrast levels.
Photogene works just as well in landscape mode as in portrait mode, so those wide photos are a snap to edit.
The point of the best iPhone apps is to add functionality that the iPhone itself lacks, and Photogene succeeds admirably. Well worth your three bucks.
Note: Photogene costs $3 and offers no trial period. This link takes you to the vendor's site. From there, you can follow the link to the iTunes App Store, where you can download the latest version of the software.