More affordable yoga
Here is an article from the NYT about how some studios are fighting back (at last !!!) against the commercialization of yoga. There are more yoga studios now that operate on a donation basis -- and they are spreading. They usually have a suggested donation of about $8-$10 per class-- but you can give more or less, depending on what you can afford. Some places let you buy unlimited yoga classes for a reasonable fee of about $100/month.
Also, check out the iPhone yoga or meditation apps. You Tube has yoga instruction too if you scroll around and some of the teachers are great.

http://www.nytimes.com/2010/04/25/fashion/25yoga.html?pagewanted=1&ref=homepage&src=me