From rosendahl in the MAKE Flickr pool:

Built from plans in Make Magazine with a couple mods. Made from a sprinkler valve and PVC (and of course duct tape!), compressed air fires the rocket high into the sky. Our rocket is make of the foam cylinders you wrap around hot water pipes (and duct tape!).

Here is a printable pdf of the rocket body and cone. Check out the article in the digital edition of MAKE, Volume 15.