What image editing software should you use other than Photoshop prefrably free

The best free image editing software that I know of would be GIMP, don't mind the name it's just an acronym for the GNU Image Manipulation Program, this program, while not as varied as Photoshop, is free to download from the website gimp.org, seriously, go through Google first if you don't believe that it isn't some weird fetish site. I've used it on a number of occasions and can vouch for its usefullness, and there should be plenty of tips online to help you get to grips with utilising it.