Ages: 17 (Catherine), 19 (Dave), and 29 (Geoff)
Location: New Hope, Pa.
2006 Revenue: undisclosed
Employees: 25
Year founded: 2005

A social networking site for teens, myYearbook.com was hatched around the family dinner table by siblings Catherine and Dave two years ago. With older brother Geoff now on board, the site has since grown from a single high school to more than 3 million members and more than 4.5 million visitors a month, ranking it third among all social networking sites in the United States, behind MySpace and Facebook.