Sandy Weill, the man who created Citigroup, Larry Ellison, founder of the software giant Oracle, and Pierre Omidyar, founder of eBay, are among the billionaires making a public pledge to give away more than half their fortunes.
Forty of the world's richest families have signed up to an initiative that was launched in June by Microsoft's founder Bill Gates and Warren Buffett, the investment guru, aimed at promoting philanthropy among the super-rich. Mr Gates and Mr Buffett are the two richest men in the US, with a combined wealth of $100bn (£63bn), and are firm friends.
The pair – who are both putting the bulk of their fortunes into the Bill and Melinda Gates Foundation, which fights disease in the developing world and promotes education in the US – have been searching for supporters for what they call "The Giving Pledge" after becoming concerned that the recession has cut into charitable giving.
Billionaire signatories have to pledge that they will give away a majority of their wealth either in their lifetime or on their death, and write a public letter explaining why. They also agree to meet annually to discuss the most effective way of making a difference.
In a letter explaining his pledge, Mr Weill and his wife Joan wrote that "shrouds don't have pockets". George Lucas, the creator of Star Wars, said he was dedicating his fortune to improving education.
"When I was in high school, I felt like I was in a vacuum, biding time," he said. "It's scary to think of our education system as little better than an assembly line with producing diplomas as its only goal. Once I had the means to effect change in this arena, it became my passion to do so "
And Mr Omidyar said he has been increasingly interested in philanthropic causes since eBay went public in 1998. "In a matter of days we went from making a modest living to landing a spot on Forbes' list of richest Americans. It was a surreal experience. But the responsibility we felt for being good stewards of that wealth was genuine – and has grown ever since," he said.
Other signatories so far include figures from the worlds of media, including the media mogul Barry Diller and his wife, the designer Diane von Furstenberg, and from finance, where those giving the pledge include the co-founder of Blackstone private equity firm, Peter Peterson, and the hedge fund giant Julian Robertson.
Mr Buffett said four years ago that he would give away 99 per cent of his wealth. He often argues in favour of big inheritance taxes, saying children should work for their own fortunes.