Chairman and CEO, AOL
Rank change: Down
It's been less than a year since AOL was spun out of Time Warner (parent of Fortune's publisher), but Armstrong has been on a tear in his efforts to transform the dotcom-era punchline into a powerhouse in emerging forms of digital content and journalism. He has slashed 8,900 jobs, and cash on hand has increased from $100 million to $600 million, even while the company has invested in local journalism ventures like Patch and Seed and made headlines by buying popular Silicon Valley blog TechCrunch.
Side project: Armstrong is a part owner in the upstart United Football League.
NEXT: 19. Esther Duflo
Last updated October 14 2010: 1:25 PM ET