Scaling a photo for iPhone wallpaper?

I know it can be done. I have the perfect picture that if it would fit correctly on the screen, it would look good. Is there a free app I can use to make it fit my screen? Or what should I do?

If it doesn't fit the screen, you need to crop it down. However, at the aspect ration phones take the picture, it should fit perfectly. But if you downloaded it, on the other hand, there will either be black bars (aspect ratio) or the image will be cropped in for you. What I would personally do is experiment with cropping first. THEN, if you can't figure something out, head in to your local Apple Store or Genius Bar (within the Apple store) and they should PROBABLY be able to help you. You could always call in to them to. If there are any apps, I haven't heard of them. Besides, I don't recommend them anyway, because they are not made by well-known developers. Therefore, for all you know, they could have viruses of some sort.

Photoshop CS5.1 or CS6