http://abduzeedo.com/reader-tutorial-how-create-awesome-action-picture-gimp

This tutorial is a remake from a Photoshop tutorial, that can be found at http://abduzeedo.com/how-create-radical-photo-sequence. It was written by Paulo Canabarro. This tutorial is intended for people that have a general idea of layer masks, as layer masks are a big part of this tutorial.