I am living in the East Village currently.  So I am going to try out places near me at first to see which is the best.  Last week I went to Yoga to the People on St. Marks this place is the closest to me, and it is also done by donation.  $10 per class is the suggested rate, but you can give whatever you have.  The proximity and the price are right, but these classes get so crowded. 

They say on the website to get there 15 min. early and I highly recommend it.  There are 3 floors of studios and they try to accommodate everyone which is great, but it gets a little close for comfort. These classes are not heated, but the way they pack people in it might as well be. I have gone back a few times and I have had different instructors each time.

I even brought 2 of my (male) roommates, and I think that they may be the only 2 people ever to have been yelled at by a yoga teacher.  So moral of their story: don't talk too continuously through the class and don't laugh too hard at other people's heavy breathing. The teachers don't like it.