I bet everybody has a great answer for this one!
My library is made up primarily of the YogaJournal / LivingArts series that features, among others, Rodney Yee and Patricia Walden. The new DVD format includes interviews and generally a modification appendix that make these challenging, Iyengar style yoga workouts more attainable.
I started with the AM / PM set at 470 pounds. It took a year to be able to do the asanas included in that program the way they were presented, but I really responded to the series. My 'Yoga for..." series now has Energy, Mediation, Athletes, Upper-body, Strenth, Flexibility, Relaxation and the new Intermediate series.
I HIGHLY recommed this series. (I also really like Dia e Brunie (sp?) on FitTV's breathing space yoga. She's a relaxed ashtanga instructor, with a vocal delivery just this side of Wai Lana, but I love her half-hour classes...and she tells you what to be doing doing the commercial break

Inhale on Oxygen is also appealing primarily because of Steve Ross, but his high energy style is not that geared toward the average novice.
Namaste,
BrianClt