Bill and Melinda Gates, U.S.Donations: $28 billion Net worth: $66 billion Early on Gates dabbled in different areas, giving

money to Harvard's computer science department, libraries, pilot high schools and local Seattle charities. His giving really took off in 1999, when he funded his family foundation with $16 billion in Microsoft stock. Since then, with further contributions from Gates and pal Warren Buffett, the foundation has become the preeminent philanthropic institution in the world. Among its main

initiatives: It will spend $10 billion on vaccines within the decade, taking on diseases from malaria to meningitis. In the U.S., education--teacher training in particular--is its main project. In April his

wife Melinda launched an effort to make contraceptives accessible worldwide, pledging $1.1 billion to the undertaking.

Warren Buffett, U.S.Donations: $17.25 billion Net

worth: $46 billion For many years Buffett insisted he would give all his money away at his death, but not before. He had a change of

heart, and in 2006 made a pledge to give more than $30 billion over 20 years to the Gates Foundation. In 2012 he turned over $1.5 billion

worth of Berkshire Hathaway stock. Perhaps even more notably, he teamed with Gates in 2010 to create the Giving Pledge, which

has signed up 92 wealthy individuals and families to commit

to giving the majority of their wealth to philanthropy. On his

birthday in August Buffett pledged $3 billion of stock to his three

children's foundations.

George Soros, U.S.Donations: $8.5 billion Net worth: $19

billion An eclectic giver, Soros has doled out $8.5 billion since 1979, backing causes

as diverse as clean-needle clinics in California and scientific research in Russia

to helping the Roma, or Gypsies, in Eastern Europe. Of the $8.5 billion the hedge fund legend has given away, approximately $6 billion has been dispersed internationally

and an estimated $400 has been dedicated to combating poverty. Recent initiatives

include $150 million for promoting transparency in governments around the

globe and $100 million to overcome barriers faced by African American boys

and men.

Gordon Moore, U.S.Donations: $5 billion Net

worth: $4.8 billion The Intel co-founder and former CEO handed over approximately

$5 billion in stock to the Gordon and Betty Moore Foundation in 2000. The foundation focuses on science, environmental

conservation and nursing education. The last category

was the brainchild of Moore's wife's Betty, who once

received the wrong injection from a nurse in the hospital.

Moore is also partially funding the construction of the

world's biggest telescope; it's in Hawaii, where he lives part-

time.

Carlos Slim Helú, MexicoDonations: $4 billion Net worth: $69

billion World's richest man has publicly stated that he feels more good can be

done from creating jobs than from band-aid charitable giving. Yet it turns

out he gave $2 billion, mostly from dividends, to his Carlos Slim

Foundation in 2006, and another $2 billion in 2010. Most of its programs are focused on digital education and

health. A $100 million gift to the Clinton Initiative project is helping pay for 50,000 cataract surgeries in Peru. With the Gates Foundation and the

government of Spain, the Slim Foundation is spending $150 million on

nutrition and disease prevention in Central America.