This transcript from October 19, 2009 lists Hefner as Director of the Board of Directors of the Center for American Progress Action Fund (CAPAF). CAP's annual report from 2010 lists her as a member of the Board of Directors.
CAPAF is the lobbying arm of CAP, and was formerly known as the American Progress Action Fund. It is also described as CAP's "sister advocacy organization." It is organizationally and financially separate from CAP, although they share many staff and a physical address. CAP is a 501(c)(3) nonprofit, whereas CAPAF is a 501(c)(4).
As you can see here, Christie Hefner has been a prolific donor to Democrats. Her father Hugh Hefner has also been a long-time donor to Democrats.
Hustler founder Larry Flynt is also a long-time donor to Democrats.
This article says that the porn industry is a small but important source of campaign cash for Democrats. That said, porn star Jenna Jameson has come out in support or Mitt Romney.
Is CAP the porn industry's favorite Washington think tank?