PaintShop Pro isn't free, but there is a demo available:
http://www.corel.com/servlet/Satelli...wnloads/Trials
Version 10 (X) is out now. It used to be owned by Jasc, and now Corel owns it. I haven't used it since Corel bought it, but it wasn't bad. Corel makes pretty good software, Corel Draw (a vector program), so I would assume it's just as good, if not better now.
If you want to go free, your best choice is probably Gimp.