Two years ago, citizens in the Arab world—fired by their ideals and visions of a better life—ignited a social movement that inspired people around the globe. In Egypt, Jordan, Libya, Morocco, Tunisia, and Yemen—the so-called Arab countries in transition—people embraced change, ushering...

By combating malaria with mosquito nets or building schools and providing basic sanitation, philanthropy is helping transform the developing world. Rich donors are devoting fortunes—many of them earned through computer software, entertainment, and venture capitalism— to defeating poverty and...