The latest class of signatories to the Giving Pledge – the billionaires’ commitment, started by Warren Buffett and Bill and Melinda Gates, to give away half of their fortune during their life or upon their death – will be announced later this morning. Among the seven new “Pledgers”: Facebook COO Sheryl Sandberg, the first self-made woman tech billionaire who now becomes just the second woman (after Spanx’s Sara Blakely) to pledge to give away the majority of a fortune she made entirely herself.

Sandberg was joined by her husband, Dave Goldberg; early Google employee Craig Silverstein and his wife, Mary Obelnicki, Kinko’s founder Paul Orfalea and his wife, Natalie; and Scottish transportation tycoon Ann Gloag. This group now swells the t

otal number of Pledgers to 127, up from nothing four years ago — but still less than 10% of the 1,650 or so billionaires that have been confirmed by Forbes. A group of Pledgers just finished their annual gathering, held this year in Santa Barbara, which focused heavily on partnering with government to maximize impact, and social entrepreneurship.

Another focus of the gathering: investing in women and girls. While Sandberg has yet to make public her Pledge Letter, which generally spells out why they chose to give and what they might support, she has been a well-known advocate for women and girls, including board positions at Women for Women International and V-Day, and she’s funded, personally and through her bestseller of the same name, the Lean In Foundation. For Sandberg, whose net worth has been hovering right around the $1 billion mark lately, gender issues in the private sector largely require private sector solutions. “Businesses are going to care about diversity not because they want to do good in the world,” Sandberg told Forbes earlier this year. “They’re going to care about diversity if it’s going to change their bottom line.”

Philanthropy, however, allows her to pursue her goals in this area in a more unfettered way. And now the 44-year-old is pledging $500 million to fuel that cause.