I just started doing the "Biggest Loser Weight Loss Yoga" dvd and it's fantastic if you're looking for a challenging power yoga type of workout. It's supposed to be a 6-8 week program with 3 levels. I've only done level 1 so far, which is 35 mins. There are a lot of warrior poses (i.e: squats and lunges!) and plank flows (i.e: push-ups!). I've definitely been all sweaty afterwards!
I'm really impressed with what a great workout it's been so far and highly recommend the dvd!