According to the FLOSSPOLS surveys done in 2004-5, only 1.5 percent of the FOSS community is female. That amount has probably increased since then, particularly if you count non-coding roles such as technical writing and marketing.
However, given that coding is central to FOSS, it makes sense that one of the first efforts to correct the imbalance would focus on teaching more women to code and providing mentoring and professional networking for women in programming careers.
Such groups have existed for years. Recently, though, they seem more numerous than ever. They include such groups as Code 'n' Splode, Geek Girl, Girls in Tech, Hacker You, Ladies Learning Code, PHPWomen, RailsBridge and Women Who Code. Some of these groups operate nationally or even internationally, but much of their work is done at a local, grassroots level.
Under the leadership of Marina Zhurakhinskaya, the GNOME Outreach program has offered internships for women with all aspects of the GNOME project. The program takes several steps that help insure its success, such as helping applicants to gain necessary skills before applying, pairing successful applicants with mentors, and teaching such cultural aspects as peer review and version control systems. In the first round of internships, fifty percent of participants continued to contribute to the GNOME project -- an unusually high rate for such programs.
In some circles, the Geek Feminism Wiki is seen as a movement. In reality, as the name suggests, the site's primary purpose has been to write and collect resources on women's issues, both in general and specifically for sub-cultures such as science fiction fandom, gaming and FOSS.
One purpose of the wiki is to act as a kind of group memory, recording incidents and individuals so that sexism is remembered. However, an equally important purpose is to analyze sexism and related forms of discrimination, and to suggest responses to them.
Look up "tone argument," for example, and you will find that the phrase refers to the common suggestion that women would advance their goals better if they were more pleasant. The article identifies this argument as an irrelevancy to any discussion and suggests how to refute it.
This kind of analysis apparently unsettles some people. In conversation, I have heard several people refer to the Geek Feminism Wiki as "scary."
However, I suspect that part of such criticism lies in the fact that, at its most effective, the wiki analyzes topics most people never think about. Probably, too, the anticipation of counter-arguments, while based on experience, can be read as arrogance.
Yet, overall, the wiki rates as one of the highest intellectual achievements associated with both recent feminism and FOSS. Just as importantly, it not only tells supporters what to expect, but makes clear that they are not alone. You can judge its importance by the fact that, sooner or later, almost every women's group in FOSS borrows resources or ideas from it.