Following from are women in tech really in tech we have:
Some things to think about before you exhort everyone to code by Miriam Posner
Which points out the important cultural aspect of why it is that women are often not coders.
If you are not a woman in tech, and wonder why there are so few... this article is for you.
So is this recent article on the recent "brogramming" phenomenon: Brogramming: just one of the girls by addabirnir from Skillcrush
She points out that "brogramming" has its intentions in the right place: it is just trying to inject some appeal into coding... but is doing so in a blatantly misogynistic fashion. (eg "without brogramming, bros might just feel like...one of the girls") and thereby alienating the very few women who are trying to break into this industry.
The important take-home message from her is "you don’t need to alienate anyone to make yourself comfortable"
Also of very distinct interest is the NYT article about Wikipedia's serious gender imbalance, which also points the finger strongly at geek culture - which is extremely male, and can be very uncomfortable for a woman.
Speaking personally on this subject, it took me a good ten years before I figured out the rules for getting along in geek society. My feminine upbringing was with an entirely different, incompatible culture. I can well understand that the serious culture shock would be offputting to the point where many women might not even want to bother continuing.
Again, I'd recommend reading all these article to get a glimpse into why this is the case.