GIMP is an open source image editing program, I use it also because I'm poor and like open source software. I'd also like a nice tutorial on how to use any image editing program really. I'm horrible with it.
Good grief, I only waited this long to see if Omega would actually post on here and help this dude. Well since I don't have GIMP I can't really help you with the program generally, BUT I can show you where you can get some really nice tuts for it Here is the link:
Just type in GIMP in the search box on the bottom and you should come up with pages of tuts last time I typed it in, which was just a couple of minutes ago^_^; I hope it helps you! I wish I could help you more but I use Photoshop CS2, I've never used GIMP in my life >.>;