I just started a meetup group for female developers in Austin. If you're in Austin reading this and you're a woman or know a woman who does development of any kind, you should check it out/pass it on!
I don't know that a women-only meetup would be any more compelling to women who don't normally come to these things. But I figure it's worth a shot. (Literally. If you get a woman to sign up for the group I'll totally owe you a shot.)