Since we were talking about free e-books I thought I tell you about another free e-book. You probably know about it but anyways: Grokking the Gimp is a free book by Carey Bunks. It’s an advanced book covering A LOT of what you can do with Gimp.
For any of you who are at least a little bit interested in graphics Gimp should already be on your radar. I know that Adobe Photoshop is more advanced, but I also realized working with both that for at least 90% of the tasks (and for my webdesign and graphics design needs 100%) is good enough.