I've recently been reading a lot about the history of yoga, and its track westward to North America and western Europe, how it's changed since its arrival, etc.
Yoga has the unfortunate problem of being rather expensive, as activities go. So perhaps it is not the (pocket/wallet) "greenest" of fitness and healthy-mind activities. But, if you search around your community, you may find that there are often less expensive places that offer yoga. Many studios have a "pay what you can" policy. Universities and community colleges offer yoga at extremely reasonable rates. Health clubs offer yoga. Even many churches and hospitals offer yoga. There is one hospital in our community that offers yoga for as little as $3 per class.
Yoga can offer numerous health and fitness benefits (body awareness, stress relief, flexibility), but I feel that one of its main strengths is in teaching and reinforcing mindfulness. Being aware of yourself and your choices is a critical skill that can often be overlooked in our over-consuming, over-anxious society. We can be so busy and make so many empty choices, yoga can almost feel like a relief. Yoga allows - and actually requires - us to be present on the mat, quiet and concentrating on only one thing at a time.
For those of you local to the Burlington, NC area, I'll give a shout out and hearty recommendation to Om Shanti Yoga. I have been enjoying their classes since August. What a great group of instructors and students.