Another vote for fitness classes! I've been doing Zumba for several months, and I love it. It's a great all-over workout, and keeping up with the steps is enough of a challenge to make it interesting. I'm sure I look pretty silly, because I'm an absolute klutz, but I'm too old to care and I'm having fun.

I ususally do a couple of Zumba sessions each week, a yoga class, and "lunch crunch" classes two or three times a week. I also work in as much speedwalking as I can--two or three miles, a couple times a week. It's definitely a time commitment, but I feel about 200% better since I joined the gym and changed my eating habits nearly a year ago.