I am only an amatuer yoga person. But doing yoga sure helps to keep me flexible and limber. Especially after working out with Cathe. My hip flexors and legs get major sore if I don't give them a good stretch. Yoga also helps with my upper body, when I get DOMS after a good hard workout.
I usually use Candlelight Yoga, The Joy of Yoga or Fat Burning Yoga. All of these are put out by Crunch. I also use Karen Voight's Yoga Focus. None of these workouts use fancy yoga terms and have very good hints as to how to make sure you are doing the poses/stretches properly.