Martin Fowler recently published a great blog post on how to get more gender diversity in IT. You need to read his post to understand this one, but in a nutshell he makes an analogy to a bag of marbles. 80 % are blue and 20 % are pink. 10 % of each colour are sparkly. As long as you have 100 marbles, you can find 2 sparkly ones of either colour. You just have to look for them.
When I read his post, I thought, "what about the marbles outside the bag." In the universe of marbles, 50 % are blue and 50 % are pink. 10 % of each colour are sparkly. So if you step outside the bag (e.g. the resumes you received for a job posting), the probability of finding a sparkly pink marble is actually greater than that of finding a blue one.
Another thought would be to get a bag of pink marbles from the factory. Then it's really easy to get pink sparkly marbles. And you'll probably get to chose amongst all the sparkly ones yourself, at least until other people clue in that this is a good way to get sparkly marbles. This is the equivalent of recruiting from women in IT meetups and suchlike. And that's not so hard.