NEW YORK — Every other month, Karlene Grabner joins about 20 women for a potluck supper that may seem like a social gathering but has a much larger purpose.

Grabner is part of a group that calls itself the GEMS — standing for Giving Empowers My Sisters. The GEMS pool their money to donate to charitable causes in their community, Oshkosh, Wis.

The GEMS, formed more than a year ago, are part of a growing cadre of charitable giving circles that gather people interested in philanthropy to pool their money and time so they can have a bigger impact than they would by donating individually.

"We've funded the symphony," Grabner said. "We funded a sports complex going in at the university — we bought a couple of bricks. ... We're looking at an environmental project."

Touched by the plight of a single mother whose three children were badly burned in a house fire, the GEMS voted their $250 collection from one recent meeting to the family's care.

QUIETLY ADDING UP

Scott Simpson, of the Forum of Regional Associations of Grantmakers, a charitable network based in Washington, D.C., said the forum has identified some 390 giving circles so far, but believes there are far more across the country.

"Many are small and operating under the radar," Simpson said. "It's truly grass-roots philanthropy."

Most of those on the list the forum has compiled have been formed since 2000, and they're located in almost every state. Often they're made up exclusively of women. And while some are church connected, most often the circles are nonsectarian and focused on community activities.

Most concentrate on pooling small donations, Simpson said, but others have gathered hundreds of members to give of their time or sponsor major fundraising. "The giving circles have given at least $37 million to charities that we know of — and we think that's just the tip of the iceberg," he said.

GEMS members, who try to donate $20 at each meeting, are organized much like an investment or book club. Meetings rotate among members' houses, and the women take turns bringing appetizers, wine and other food.

"Generally, five people are asked to bring forward a cause that they feel some money should go to, and we all talk about it," Grabner said.

Some giving circles are created by major charities. Elise Lee, a division director of the United Way of Central Maryland in Baltimore, said one of its circles is made up of more than 100 women who each donate $10,000 a year or more. Another circle is for those committed to giving $1,000 a year each, and now has some 3,000 members. "Both provide opportunities for women to come together," Lee said. "And it gives us a chance to educate them to opportunities to get more involved in philanthropy."

CHOOSING THEIR CAUSE

Some giving circles are national groupings, such as Dining for Women, dedicated to improving the lives of women and children in developing countries. Others have an ethnic bent, such as the Latino Giving Circle in Chicago and the Asian Women Giving Circle of New York City.

Some, like the Cleveland Colectivo — whose several dozen members are mostly young professionals and donate about $400 each a year — try to break new ground close to home.

In one year, the Cleveland Colectivo raised more than $7,000 that went to an internship that creates neighborhood murals, a community program for refugees, a car-sharing service, and a "learning" garden to be planted and maintained by neighborhood youths.