This was an interesting forum to read...so I thought that I'd add my two cents too.
From my experience, very few women "bulk up". however, I am one of the few. I was a competitive track athlete for 6 years; my diciplines were hammer throw, discus, shotput and javelin. When i joined my college team, I weighed 160lbs with 19% body fat (at 5'9). After my first eight months, I weighed 175lbs with 16% fat. I was squatting over 350lbs, benching over 200, and power cleaning over 200 as well...but I looked great....you never would have guessed that I was 175lbs.
I was one of the few women that puts on muscle mass easily. Every other girl on the team spent as much time in the weight room as I did. Even my fellow throwers never put on mass like me. In my 6 years as a compettive athlete, there was only 2 other girls that were in my club, or on my teams, that were the same as me: a mass builder. One was a runner, and the other was a heptathlete. Because extra weight would greatly affect their speed, they had to limit their time in the weight room and spend more time on the track. Since I threw, extra weight wasn't as big of deal for me, but my coach was careful to keep me under 175lbs because there comes a point where too much hinders you...you have to be able to "wield" what you have.
My point is that I am a freak. Very few women hypertrophy the way that I can. My husband envies my ability to be able to develop mass and strength easily....chalk it up to chucking bails on the farm, or just a genetic lottery....I don't know, but from my experience, most women can train like a man and not get huge. It's all about finding out your "combination". Now that I train for triathlons, extra mass is highly inconvienent so I limit my time in the weight room, and study yoga to balance my strength training.
Most women are terrified of "bulking up", but from what I have seen and experienced, it's not common for women to have the same muscle growth as men. Even me, a freak as far as chicks go, never looked like a man....not even close.

I was, and still am, a hottie.
Lifting weights just made me look better...and it still does....it just improves upon what nature gave me. What I gain in muscle, I have lost in fat. Women have to get it out of their heads that lifting weights is going to make them into men...it's not...not unless they are taking roids or growth hormones on the side. Weight training has so many benefits....from a higher bone density to a great ass (like buff hottie's).
Women can greatly benefit from weight training. Let them know that their chances of being like me are slim to nil. I have only known 2 others: and they were hot too, so don't worry so damned much about it. If you do end up being a "bulker", then you can always tweek your training to accomodate it. Don't be so short sighted that you miss the big picture: weights training will improve you.