Oracle's Jessica McKellar and developer Asheesh Laroia recently led a session at PyCon 2012 on the subject of creating more diversity in the programmer community. The case study in question was The Boston Python User Group, which has worked diligently to create a membership composition that is 15% women - quite uncharacteristic for a user group.
Here's the session itself:
And here are the slides. This session is worth exploring by anyone interested in tactics for increasing programming community diversity.