This is the html version of "grokking the gimp", an excellent introduction to the gimp and to image processing in general. it covers the basic gimp tools, layers, selections, masks, color spaces, color manipulations, photo touch-up and enhancement, compositing, shadows, punch-outs, bevels, and how to use the gimp to create online content (animated gifs, clickable image maps etc).

"grokking the gimp" is very readable and includes lots of example graphics.

it is recommended that you use a browser with proper support for pngs to read this book; newer versions of mozilla (or galeon) are known to work.