Here was a post I made on my personal journal that I thought the weight loss support group might find helpful.
It's important to track body fat % (not the same as BMI) for anyone that is doing both cardio and strength training. Doing strength training will obviously add muscle. Muscle is 17% denser than fat, and while a pound of muscle weighs the same as a pound of fat, when the density of both is compared to the volume inside a container (say ONE butt cheek), the same amount of muscle as compared against fat will actually weigh more. So if you're doing strength training AND trying to lose weight at the same time, it's important to measure body fat %. That "plateau" you might be experiencing with weight may not be a plateau at all when additional metrics are used. Sure, if you're a horse jockey trying to lose weight (no matter where it's from), then a plateau is a plateau, but if you're goal is to lose fat, gain muscle, speed up your metabolism and become generally more fit, then you need to start tracking body fat %.
You can measure body fat % several ways, look here http://www.new-fitness.com/body_fat_analyzing.html for a good article. Pay close attention to the discussion on Bioelectrical Impedance. This is going to be the easiest way for you to measure body fat %. They usually have devices at your local gym (look something like this http://healthstore.securenetworkserver.com/images/products/Omron-HBF-306C_large.jpg) or you can buy a nice scale that does this through your feet instead of hands (http://www.omicroninternational.com/images/prob_bs1701_1_.jpg). I've heard tanita is one of the best home scale brands, for the money.