At 35, Saul Griffith is already a prolific -- and eclectic -- inventor and entrepreneur. He has helped launch a half-dozen startups around his creations: a portable machine that makes cheap corrective lenses; a hand-powered gen-erator for recharging handheld devices; Instructables, a Web site for sharing do-it-yourself projects; and a play-ful science education site for kids. His latest company, Makani Power, is building huge kite turbines to convert high-altitude wind into energy (Google's investment: $15 million). "I very much enjoy the process of creating something new," says Griffith, an avid kite surfer, "so my hobbies get entangled with my work." -- by Chuck Salter