The GIMP has a well-deseved reputation for being massively powerful and user-hostile. Has perhaps improved a bit over the years (less hostile now that it has a user interface) but it's still more of an overflowing Craftsman rolling toolbox than an application. Unfortunately, if you need all the trimmings it's probably the only thing out there that can compete with full-up PS.

If you can live without The Whole Enchilada, there are numerous options. PS Elements, obviously. Also some free stuff Paint.NET [www.getpaint.net] and Irfanview [www.irfanview.com] are useful. In the Pay$$ realm, Corel [www.corel.com] is still out there, and I like ACD Canvas [www.acdsee.com] (though at home I have an older version, from back when it was affordable) because it covers nearly the whole CS suite and a bit of CAD in one application even adding some GIS capability for a bit extra. There are also some oddities out there like ImageJ [rsbweb.nih.gov] (Your Tax Dollars so why not check it out) and a crowd of others in the Mac realm that I'm not familiar with. An interesting site that sometimes addresses things non-PS is Plugs 'n Pixels [www.plugsandpixels.com].