I've finally gotten around to looking into exercise programs. Myself, I've just been walking, but the cold temperatures, I gotta say, put a major damper on that plan. I use Yoga as my next favorite thing - it's meditative, calming, centering, strengthening if you do it right, and provides an extraordinarily low impact rate on the body while you're exercising.
I think that Tai Chi would also offer the same benefits as Yoga and I'd like to learn it, but find that my body is too unwieldy still to learn the graceful dance-like poses that flow one into the other.
Recently, I've heard about a different set of exercises, 15 minutes a day, called T-Tapp. It's an interesting set. I've not yet tried it, but wanted to alert you to it's existence. The link goes straight to the "try" section that shares several of the different exercises. If you like it, they encourage you to purchase their DVDs, of course.