Hmmm...a couple of seperate issues. I've started two women's cycling groups; here's my $.02:

Recruiting women who actually own and ride bikes: I agree with the idea of the "women's only" ride. Advertise by making fliers and taking them to all of the local bike shops, plus anywhere athletically-minded women congregate (gyms etc.). Post a notice on your club's website. Keep your ride on the same day/place. Consistancy is the key. We have picked up more than a few riders by just having them see us in the same place at the same time. Eventually you can "phase them in" to the regular club rides.

Recruiting "spinners" (women who only ride indoors): a bit more difficult. Many of them don't even own bikes. It helps if you have a few bikes (including a few small sizes) to lend. Offer to take them out for a spin. Make it fun. Pick a scenic, lightly-trafficed loop. Encourage them to come on your "women's ride" (see above).

Recruiting racers: don't forget to have cards or at least a pen/pencil with you at all races. You want to be able to exchange contact info easily with other women who are within a few hours of you for training rides.

I am happy to report that these methods have worked for me. Good luck.