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Lesser-known donors include 36-year-old John D. Arnold, the creator of EnronOnline, investor Ronald Perelman and Ken Langone, former director of the New York Stock Exchange and financial backer of the Home Depot.

One of the more shocking commitments came from Larry Ellison, the co-founder of Oracle, who gained the reputation as philanthropist bad boy when he withdrew a large donation from Harvard over the resignation of the university president, Lawrence H. Summers.

In a note to the Giving Pledge, Mr. Ellison wrote that he had already given a large portion of he wealth to “charitable causes” and intends to give away even more in the future.

Media mogul Ted Turner, who also pledged his support and wrote, “I don’t measure success in numbers, but I consider my contributions of more than 1.3 billion dollars to various causes over the years to be one of my proudest accomplishments and the best investment I ever made. Those dollars have improved lives, saved species, fought disease, educated children, inspired chance, challenged ideas and opened minds; and at the time of my death, virtually all my wealth will have gone to charity.

“Looking back, if I had to live my life over, there are things I would do differently, but the one thing I would not change is my charitable giving,” he said.

In another letter, Mr. Bloomberg said that he decided to give because it is a way to show his children that he cares.

“If you want to do something for your children and show home much you love them, the single best thing — by far — is to support organizations that will create a better world for them and their children. And by giving, we inspire others to give of themselves, whether their money or their time,” he wrote.

According to Sean Stannard-Stockton, CEO of Tactical Philanthropy Advisors, the pledge, while directed toward billionaires, also will have an impact on everyday Americans, partially because of the commitment of Mr. Gates and Mr. Buffett’s celebrity. He also called the pledge list “quite amazing” even though he is not familiar with a few listed.

“I think the much bigger ramification here is the potential for it to influence the way every American gives,” he said. “Bill Gates is only responsible for 1 percent of annual charitable giving. Everyday Americans, however, will see this and it will motivate them to give more.”

The list also will encourage more of America’s wealthiest to give, he said.

“The activity by Warren Buffett and Bill Gates is very influential. We have people like Mark Zuckerburg of Facebook and the guys at Google who cite Warren Buffett as an example of how they manage Google’s finances,” he said.