44. Marissa Mayer
VP, Search Products and User Experience
Google (GOOG)
2008 rank: 50
Age: 34
When she joined the startup in 1999 as the first woman engineer, Mayer gave it a 2% chance of succeeding. Now she not only directs the look and functionality of the $14 billion search engine, she's also behind more than 100 products, like Google Earth and Google Chrome, the Internet browser and operating system that's challenging Microsoft Windows.
NEXT: 45. Lynn Elsenhans
