I LOVE yoga!!!
I have great results--it's very calming, relaxing, and it's good for you. My posture has greatly improved and my back/neck rarely hurts anymore. My back is usually the worst part of my body, for some reason despite being healthy and young, my back was always troublesome. Even in high school I'd throw my back out sometimes. After starting yoga around age 18 or so, my back has only gotten better.
I mainly do yoga videos from the Gaiam website (I do the Rodney Yee videos) and I absolutely love them. Rodney Yee is a great instructor. I also have the Yoga X video from the P90X series (thanks to a friend who hates yoga--she thinks its boring). I also do some yoga videos off of youtube if I am bored with the videos I have on DVD. I like the yogatoday channel on YouTube.
I also go to a Sikh temple that's
3HO affiliated. 3HO members are
really passionate about Kundalini yoga. They swear by it. So, due to peer pressure, I've tried it a little. It looks silly, but it's actually quite difficult. I don't practice Kundalini yoga regularly (I think it's terribly boring!) but I know its really good for you, because the breathing exercises required to do it really made my lungs feel great the few times I've tried the practice.
There's tons of different kinds of yoga, so try a few and see what works best for you.