Hello, and congratulations on taking the best step possible to a healthier mind and body!
If you don't want to invest in dvd's just yet, you can find free yoga workouts here:
ExerciseTV
I like this yoga/fitness fusion one based on Ashtanga Yoga. Its 20 minutes and covers everything:
Cardio Yoga - Workout Videos - ExerciseTV
If you want to try out Kundalini, a totally different kind of yoga, here's a nice workout from google video:
YouTube - Introduction to Kundalini Yoga
I love both styles, but Kundalini more :-) Yoga is the best, it frees the mind, tones the body, unites our inner and physical aspects and brings focus and happiness. Enjoy your journey!