Since I promised to post this, here's Christina Haralanova's master's thesis on women in the open source community: http://www.ludost.org/content/release-10-womens-contribution-free-and-op...
The document is in French. I hope to find the time to write an English summary at some point, and Christina also hopes to translate the entire text if she finds the time and/or money to do so. In the meantime, here it is for those of you who do read French.
Very, very quick summary: women actually contribute far more to the open source software community than most people realize, but as men make up a disproportionate number of the lead programmers on most projects, women's work tends to not be as visible or valued.

Comments
I just cross-posted this to
I just cross-posted this to the Drupalchix group http://groups.drupal.org/drupalchix - hope that's ok, I think there will be a larger audience of interested people there!
Reading this makes me very happy to work with two awesome programmers who are women and lead lots of our projects! We have 7 male devs and then my boss (male) and I (I'm a project manager) - I think it's a decent balance in this field, despite not being too close to 50-50.