Bill and Melinda Gates Foundation

This month, 12 more billionaire families committed to donate at least half of their wealth to charity by taking the Giving Pledge. Here are introductions to some of the new signatories and their pet philanthropic projects.

Today's philanthropists are increasingly uncomfortable with the "write-a-check-and-forget-about-it" model. From Bill Gates to Philip Berber, they are taking a more active role in the way their money is given and the ways in which it is spent.

Microsoft Chairman Bill Gates has cut his stake in the world's largest software maker -- which he co-founded -- by 13% over the past year, InformationWeek reported. In the last five years, the company has delivered far lower returns than Apple or Oracle.

The Microsoft co-founder and philanthropist recently criticized school pay structures, urging the 50 state superintendents of education to end teacher pay increases based on seniority and education level, and reward them based on excellence instead.

With an estimated net worth of $1.5 billion, the son of a Bronx, N.Y., plumber is now donating the bulk of his fortune to charity. Cooperman's aim: to help "those that are disadvantaged to experience the American dream."

Warren Buffett turns 80 on Monday, an age at which most people have been retired for a decade. This seems as good a time as any to take stock of a remarkable life in business.

Warren Buffett's annual gift to the Bill and Melinda Gates Foundation rose 28%, to $1.6 billion from $1.25 billion last year, as Berkshire Hathaway shares jumped 35% over the last year.

Detroit's Justin Bullock must know what it's like to win the lottery. Except for the Renaissance High grad, it's his talent, and not luck, that led to him being offered a total of $1.8 million in scholarships. The 17-year-old not only was recently awarded a Gates Millennium Scholarship to pay for...