• One Percent Foundation: Aimed at young adults in their 20s and 30s, the San Francisco-based group pools donations — ideally, 1 percent of annual income — and members vote on where to donate, based on categories (education, environment, health, global aid, poverty). http://www.onepercentfoundation.org/
• The Giving Pledge: Started by Warren Buffett, and Melinda and Bill Gates, it asks U.S. billionaires to commit to giving away half of their wealth to causes/charities they support. To see signed letters from some of the 92 individuals and families who’ve taken the pledge: http://www.givingpledge.org
• Giving Circles: The Forum of Regional Associations of Grantmakers has how-to tips and resources for starting a giving circle; http://www.givingforum.org
• Giving Circles Network is a grassroots group: http://www.givingcircles.org