Eleven billionaires added their names this week to the effort by Bill Gates and Warren Buffett to donate half their fortunes to charity, bringing the total to 92.
The newest members of the club include Netflix chief executive Reed Hastings, Intel co-founder Gordon Moore, and Charles Bronfman, the Canadian-born former head of Seagram.
The Giving Pledge, announced in 2010, was launched by Microsoft mogul Gates and investment guru Buffett who want to convince the richest people in the country to give 50 per cent or more of their fortune to charity.
The group includes CNN founder Ted Turner, New York Mayor Michael Bloomberg, Oracle co-founder Larry Ellison and Hollywood director George Lucas, as well as Buffett and Gates.
"We've said from the beginning that this is a long-term effort, so it's exciting to see continued progress over the last two years," said Gates, who is co-chair of the Bill & Melinda Gates Foundation.
"This new group brings extensive business and philanthropic experience that will enrich the conversation about how to make philanthropy as impactful as possible. Their thoughtfulness and deep commitment to philanthropy are an inspiration to me, and I'm sure to many others as well."
The newest members also include Manoj Bhargava, India-born founder of 5-hour Energy; and Dan Gilbert, founder and chairman of Quicken Loans and majority owner of the Cleveland Cavaliers.
Also pledging were Peter Lewis, chairman of Progressive Insurance; Jonathan Nelson, founder of Providence Equity Partners; Jorge Perez, chairman and CEO of The Related Group; Albert Lee Ueltschi, founder of FlightSafety International; and Symphony Technology Group founder Romesh Wadhwani.
New pledges also came from Claire Tow, co-founder one of a major cable television company, and husband Leonard Tow, the CEO of New Century Holdings.
Lewis said in his pledge letter that he would make donations aimed at "promoting a healthy democracy, broad civic participation and public policy - from the support of progressive think tanks to leadership training for public servants, to investigative journalism, ethics in government, and a democratic media."
He added that another effort he would fund is "is taboo for most philanthropists yet exemplifies disastrous public policy... our nation's outdated, ineffective marijuana laws."
Lewis said he has already funded efforts to enact laws that give patients access to marijuana as relief for pain and nausea and has "made no secret of being one of those patients myself, using marijuana to help with pain following the amputation of my lower leg."
"A majority of Americans are ready to change marijuana laws, yet we continue to arrest our young people for engaging in an activity that is utterly commonplace," he said.
Bronfman said in his letter that philanthropy "is in the DNA of my family," adding that his parents were active participants in Jewish, local Montreal and Canadian charities.
"The dining table conversation was a place for discussing what was important to them in that world - it is no surprise then, that each of us has contributed to society."