A collection of 16 of America's richest who answered the call to donate at least half of their fortunes. (Donors' worth from Forbes.com.)
Warren Buffett, CEO of Berkshire Hathaway Inc. Worth: $47-billion.Nati Harnik
Larry Ellison, Oracle CEO. Worth: $28-billion.Paul Sakuma
Michael Bloomberg, New York Mayor. Worth: $18-billion.Pool/Bloomberg
Paul Allen, owner of the Portland Trail Blazers and founder of SpaceShipOne. Worth: $13.5-billion.Win McNamee
Eli Broad, art collector. Worth: $5.7-billion.Michael Caulfield
Pierre Omidyar, EBay founder and chairman. Worth: $5.2-billion.� Tim Shaffer / Reuters
George Lucas, director. Worth: $3-billion.LUCAS JACKSON
David M. Rubenstein, Co-Founder and Managing Director of The Carlyle Group. Worth: $2.5-billion.� Lucas Jackson / Reuters
Jeff Skoll, Founder/Chariman/CEO, Participant Productions. Worth: $2.4-billion.Scott Wintrow
Philanthropist David Rockefeller. Worth: $2.2-billion.Brendan Smialowski
Peter Peterson, Senior Chairman of the Blackstone Group. Worth: $2-billion.� Larry Downing / Reuters
Ted Turner, Turner Enterprises Inc. Chairman. Worth: $1.8-billion.PHIL McCARTEN
Venture capitalist John Doerr. Worth: $1.7-billion.� Dino Vournas / Reuters
Barry Diller, IAC/InterActiveCorp CEO. Worth: $1.2-billion.RICK WILKING
T. Boone Pickens, founder of BP Capital. Worth: $1.1-billion.PHIL McCARTEN