Gone are the days when the most fun you could have with helium was to inhale it and talk like Alvin the Chipmunk. Now you can ride a 21-foot balloon inflated with helium. Push off the ground and you'll rise up to 100 feet and go as far as 400 yards horizontally before touching down. It's pricey: $11,900 for the Parabounce through Hammacher Schlemmer or at www.parabounce.com. Celebs Katie Couric and Coolio have gotten high on the hobby, which can morph into perilbouncing—without friends to hold long tethers attached to the balloon, you could bounce too close to the clouds.