In browsing through iTunes there are hundreds of yoga podcasts. It can be a little overwhelming. There are asana classes of all different styles. Recently I've been drawn to the lectures and interviews (probably from needing something to do while sitting in front of a computer all day). Anyway, here are some of my audio favorites:
Kino MacGregor, Ashtanga Yoga Awareness: covers different aspects of the practice, quite a few Q&A talks with students and some interesting stories.
Yoga Peeps: interviews with different yoga teachers from all over the world (83 at current count). The teachers are asked (mostly) the same questions and each teacher has a different reason for practicing and a different approach to teaching.
iHanuman: Interviews, lectures, discussions, and a few classes, on different subjects, from the Yoga Sutras to a story of Hanuman.