Weights have always been a part of my exersice routine, even heavy (I'm not sedintary I just ate too much!) I have never noticed a slow down in my weight loss because of it but I've never tried without it and won't want to. It's makes cardio easier, your posture better and flab is flab no matter what your size.
I would have to second what Drina said, it's a real myth that weights make you heavier. Most of us here are doing fitness competitions or bodybuilding so it really isn't likely to put on tons of weight. I'd check out the fitness forum, those ladies have a lot of really good info.
I have a Fitness Blog
and it's where I hang out and write about weight loss, fitness and nutrition for those of us just beginning the journey to health.
Weight - May 14-December 23, 2009
Starting weight: 223lbs
Ending weight: 140lbs
1 year and counting!