This is the "Industrial Grade Human Powered Paper Rocket Launcher" in use at the LEAF festival in Black Mountain, North Carolina.
Notice how the launcher is tall enough that young children can place their paper rockets on the launcher without putting their face in front of the launcher. The idea here is that older kids are smart enough not to put their face in front of the launcher.
Rockets are made from a half sheet of 8.5x11 "card stock" paper and can be launched many times. Rockets that are built well will fly 50 yards!
Download build-it-yourself plans at www.TomHeck.com