My first yoga tape was Crunch Joy of Yoga, which I loved and did for about 3 weeks. THen I got Kundalini with Karen Carleson (sp?) which is more mystical and relaxing...but the poses are nonetheless challenging (it's way long, tho, 75 min) Those are my gentle yoga tapes.
For strenght building, I love YogaZone Power Yoga with Lisa Bennett. It is very challenging, and I still, months later, do it once a week min.
I really like Brian Kest as well for "hot yoga" (I thought it was really funny someone found him creepy,but I can see the potential)
I don't care for Rodney Yee. I find the transitions between moves "choppy" and his voice grates on me. I just never seem to care for the combinations he puts together, either, although some love him.
This is my thought-
If you like Crunch, you'll like Kathe Smith, Karen Voigt, the beginner YogaZone series, and Ali.
If you like powerful moves, you'll probably like inter/adv YogaZone, Baptise, Kest, and maybe Yee.
See if your video store has one for rent. If not, try the beginner first. If you're not challenged, move on to an intermediate.
I think you will love this as an addition to your routines. I really look forward to my yoga.