Adobe Photoshop might be the most famous and well known of the image editors out there, but it's also the most expensive. For quite a few years now GIMP, an open source image editor, has gathered quite a large following. Because it's better? No, of course not - because it's free!!! And the latest incarnation, GIMP 2.5, is in beta at last waiting for you to download it and give it a go. It might not be quite up to Adobe's offering, but it's still a very powerful tool, and with so many plug ins available it will probably serve your needs perfectly well.