A recent GeekDad post mentioned a UK company that will send you a cardboard rocket for 30 pounds (around $US62) plus shipping. For those of you who found that deal less than titillating, I have a better deal for you:
A company called Mr. McGroovy’s Box Rivets sells kits for building cardboard castles, pirate ships, and other designs. Basically you supply the cardboard and McGroovy’s supplies the instructions, patterns and rivets. The latter are the company’s signature product. They are plastic attachments that permit you to connect two pieces of cardboard far more efficiently than tape or staples. In addition, they are easily removable (with a special tool) and reusable.