Judy Estrin's Unfailing Eye for Opportunity

Judy Estrin's life resembles an entrepreneur's fairy tale. In 1981, at age 26, she founds her first company -- which goes public four years later. After selling that, she starts a second venture, which does an IPO in 1992. Then Estrin moves on to startup No. 3: Launched in 1995, it appeals to Cisco Systems (CSCO ), which buys it in 1998 for $84 million in stock. And Cisco makes Estrin its chief technology officer.

The bursting of the Internet bubble threatened to ruin this Cinderella story, but it didn't daunt Estrin. After leaving Cisco in 2000, she found funding for the company that becomes the mother ship for three spinoffs. She got the money, she explains, because she is a conservative entrepreneur: "I'd rather take a calculated risk than shoot for the moon with a 10% chance of success."