Been thinking these guys stuff is cool for kids for a while now so thought I'd share it with you.
Howtoons: The Possibilities Are Endless, great graphic novel style kids science/craft/make-it book. Instructions for making PVC Marshmellow Gun, Soda Bottle Rocket Launcher, and more in the book.
Web-site also cool. http://howtoons.com/
I used some of the posters I bought from them at MakerFaire in Austin, as prizes at a scout event. The boys were groovin' on them.