An interesting article entitled "Kids, Do Try This at Home...We built a backyard cannon, and you can, too" appeared in the September 2007 issue of the Electrical Engineering magazine: Spectrum. Since so many of us enjoy this stuff, here's a link to the article online:
http://www.spectrum.ieee.org/sep07/5483 Who wouldn't like to try some of the projects in the book cited. (Do pay careful attention to the safety issues it discusses before trying projects).