I like the Yoga Journal series of videos. Try "AM/PM Yoga" or "Beginners Yoga" - nice intros and fairly gentle. If you want a more intermediate video I like the video called "Total Yoga" (it's not by Yoga Journal), but you can find it pretty easily.
I like the Yoga for Relaxation tape, but you need alot of props and no kids around!
I would also avoid power yoga videos - unless you have an instructor watching your form you could risk injurying yourself.