Working in FE, I've worked with a higher proportion of female developers than others that have posted here. In my last place it was 1 girl out of 6 people that could be called developers, in my current place both my developers are female (I'm a boy but don't get much development time).
Education does play a (bad) part in this. At a young age there are about 45% of girls doing SMT (Science Maths and Technology) subjects, this participation drops steadily through A-Levels, Degrees and still further into business. What is really needed are some big name women who have done well in the industry (Bill Gates, Steve Jobs, Google, Facebook founder types). However, if women aren't in industry in the first place to be promoted it's a little chicken and egg, when trying to inspire others to start their own companies.
Some of the comments were saying that girls are better developers/project leaders/etc. I think in general this is true but it's not that girls are better technically, where they have the significant advantage is from a social and communication point of view.
A significant minority of male developers attitudes suck. More would go further if they stopped the “Not my job” attitude, thoughts that daily showers are optional, decided that techno babble is better than “I don't know but I'll find out” and understanding that development is actually quite easy.
This is very generalistic, there will be awful female and great male developers.