In the West, it seems to me, Yoga has become another way we can obsess about our bodies and our health. To be fair (as a personal trainer/strength coach) I often recommend yoga classes to my clients to increase their flexibility, balance, and core strength.
But traditional yoga has so much more than this to offer, if only we in the West might slow down and learn that body and mind are NOT separate and that training the body is a way to train the mind.
This video takes an overview of yoga and its 5,000 year history (although I would wish the speaker might have looked a little more at the spiritual than the physical benefits, although she does a nice presentation of the spiritual ideas).
Sudha Prathikanti, Associate Clinical Professor of Psychiatry at UCSF, presents an overview of the history and philosophy of yoga, including its measurable benefits to your health. She also provides a short demonstration of proper yoga breathing.