Think of the GIMP, the GNU Image Manipulation Program, as open source Photoshop (OK, OK, I know - Photoshop is all powerful and is the greatest program ever in the world and the GIMP sucks compared to Photoshop and I am a fool for even daring to suggest that the GIMP even compares to Photoshop. There, did I just reduce 90% of the angry emails I'll get? I think so.) But anyway - think of the GIMP as open source Photoshop. It allows you to manipulate images in all sorts of cool ways, far more than my non-graphical-understanding brain will ever comprehend.

There's a book out there called Essential GIMP for Web Professionals, and evidently it's got a companion web site. The web site contains exercises & instructions, a reference to perl commands associated with the GIMP, keyboard shortcuts for the program, errata for the book, an FAQ, and, of course, all the code mentioned in the book. Even if you don't own the book, the site would still be worth checking out and maybe even adding to your del.icio.us bookmarks.