GIMP
Have you ever wished there were a free version of Photoshop? Well, there is — kind of. It’s called GIMP, and it does a good job of such tasks as photo retouching, image composition and image authoring. OK, it’s is not exactly Photoshop, but it you may find it comes close enough. And in case you were worried, GIMP no longer requires that X11 be installed on your Mac.