Rodney Yee. My favorite is his Yoga for Strength. I also really like Power Yoga Total Body. Yoga Burn is good, but in a different way - very slow and relaxing. I want to try Ultimate Power Yoga next but don't have it yet.
One reason I like Rodney is that in the DVDs I have, it's just him doing the routine. I'm able to concentrate and really get into it, instead of watching the instructor bounce all over the room correcting other people's poses, etc.