There are three easy steps to getting more girls into gaming
1) Don't be a creep, make sure your group isn't made of creeps. Potentially the hardest step! We all know someone in the local gaming community that we do not want to associate ourselves with. Unfortunately, we still do. That's the catch - it takes just one creephat to inflict the stigma on everyone around. Cruel as this may sound, distance your game from the creepers - or better yet, confront the guy and flat out say, "Look, you need to cut back on the <whatever> comments, ok?" Don't just quietly hope problems with magically disappear on their own. Who we associate ourselves with is how we're seen, and if you don't want to associate with someone, then don't.
2) Don't be a creep, stop thinking of them in terms of gender. Don't whinge that all the scaaaaaaaaaary numbers are going to frighten the innocent and pure damsels you wish to bring into the fold, because oh my god that's so freaking creepy. When you try to build your idea around "Well they're girls, so, you know, they're different," guess what? That's creepy. Imagine yourself trying to explain that to the person in general. "We need to treat you differently because of your genetalia." Can you think of a way of saying it that isn't creepy?
3) Ask them. Human beings are individuals, regardless of ethnicity, gender, sex, religion, culture, race, etc, etc, etc. Women do not have one massive hivemind. Ask individuals what they like - you know, the same thing you'd (hopefully) do for new male gamers. And that's perhaps the most hilarious(ly depressing) thing; people at times whinge about how women just want to talk and roleplay out and never have combat, but I guran-damn-tee you that your male players want to do that stuff too. We dudes don't just want all hack and slash all the time! In fact, no small number of male gamers simply aren't into a lot of combat at all!
So why is number 1 the hardest? Because gaming itself has built the stigma around itself willfully. Chainmail bikinis, damsels in distress, crude pinup art, etc, etc. People love to point at loincloth barbarians to claim it's even, but it's not. Men in fantasy art are traditionally hyper-masculanized. Their strength and power is accentuated. Rippling biceps and stanecs of authority and whatnot. Women in fantasy art are traditionally hypersexualised. Plush, open lips, Swelling breasts, swayed back, you know the drill. Imagine if Conan was drawn in such a way - it would be ridiculous! The same problem hits video games. People look at female gamers and say "Well they play the Sims, clearly that's the only type of game they like," and then ignore that every other game has you playing a big buff manly macho space marine who runs around and waves their dinglybits at aliens nonstop. The Sims lets a character at least be female. is it no surprise that one of the more popular genres with female gamers lies in RPGs, especially western RPGs where you can create your own character?
Claiming that only guys play games is a self fulfilling tragedy. The more you believe it, the more you, consciously or unconsciously, build games to target only men, which draw in mostly just guys, which only fuels the belief. Let's not forget the hilarious sales flop from TSR that was the Heartquest books.
Now, it's not all gaming's fault. Certainly the hypersexualization in society as well as the still existing cultural norms that force gender roles are a problem. But dammit all, we were born as the sub-culture for people who didn't fit in - isn't it our job to fight against the norm we dislike so much?
You want to bring more women into gaming? Start accepting them. Stop seeing them as "girl games" and see them as "gamers."
Personally, I'm waiting for the topic on how to bring more men into different types of gaming. Oh, wait, even better - how to bring more transgendered people into gaming. Now that one will be fun!