An interesting talk by Alyssa Wright on the gender gap at OpenStreetMap:
http://vimeopro.com/openstreetmapus/state-of-the-map-us-2013/video/68098504

Wikipedia is referred to a few times in the talk. There are many obvious parallels and some relevant insights. Also a tool to measure participation on mailing lists in different ways, including by gender (from 16:54).

Best
Bishakha