As the title says, advanced spud guns. The site includes plans for spud guns from an experienced builder. The highlight of the site, which the link points to, is a huge spud gun based on the revolver design (i.e. old west 6 shooter, magnum, etc), and plans are included. Link. Thanks Eric! If you wanted to get started a little slower, check out MAKE Volume 03.
HOW TO make Advanced Spud Guns