If you want something nearly as robust as photoshop, with a lot of automated features that do a really nice job (teeth whitening, skin smoothing, exposure, etc) try Corel's Paint Shop Pro X3 photo. It's easy to start with, and as your skills progress it offers all the same manual adjustments as photoshop at a fraction of the cost. It goes on sale regularly for $59 from Corel's website and there's a thirty day free trial to see if it's really something you want to invest in. The learning curve isn't nearly as steep as gimp either, though gimp is the best free choice.