If you are interested in a trully comprehensive traditional yoga study course, then check out Yoga Vidya Gurukul's website and their offerings. The website itself is quite comprehensive with hatha yoga and pretty comprehensive pranayama information. If you are looking to learn yoga in a more traditional Hindu or Indian context, this place looks promising. Do check out their website, yogapoint.com, its information offering is extensive though mainly text based. As a reference for yoga teachers and adept yogis this is a very useful website.