Yoga Spirit offers lectures by top-knotch yoga instructors via the phone at a modest cost (about $20 per hour):

Yoga Spirit's tele-classes are live, interactive training classes conducted over the telephone through state-of-the-art teleconferencing bridge systems. You will receive timely knowledge, tools and techniques over the telephone that can benefit your life, teaching, practice and business immediately.

Among the teachers participating are Judith Hansaon Lasater, Amy Weintraub, Elise Miller and Paul Grilley. Lat year they had Shiva Rea. Some of these lectures are for fellow yoga teachers who want to get insight into teaching certain techniques, but I could see any yoga practitioner get a lot out of the classes. If you are in a region that does not have many big-name teachers coming through your area and you can't afford to go to a retreat or a yoga conference, then this would be a great chance to hear some interesting yoga experts.

If you can't make it to the lecture at the appointed time, you will still pick up the class by listening to a recording.