RALEIGH, N.C. -- When GlaxoSmithKline bought Todd Stiefel's family business for $2.9 billion last April, he began to think about what to do with the rest of his life.

Stiefel wanted his windfall to better society. Like many modern philanthropists, such as Bill and Melinda Gates or Warren Buffett, Stiefel is not motivated by religious zeal. In fact, Stiefel has become one of the country's biggest benefactors of atheist causes.

Last month, Stiefel gave $500,000 to the Secular Coalition for America, a Washington-based coalition that lobbies on behalf of 10 groups of atheists, humanists and agnostics. That's on top of two smaller gifts to two of the coalition's members: a $100,000 grant to American Atheists and a $50,000 grant to the Secular Student Alliance.

Stiefel's generosity is not limited to atheists. Last week, he donated $20,000 to the American Civil Liberties Union of Mississippi so it could sponsor a high school prom after the Itawamba County School District canceled the dance rather than allow a lesbian to bring her girlfriend as a date.