I find Yoga to be one of the best forms of exercise to help ease stiffness and aches that so often accompany middle age. After tiring of my limited yoga tapes from the 90's I was happy to find the site http://doyogawithme.com. It has a large selection of  yoga videos ranging from beginner to intermediate which state the degree of difficulty and describes the work out. You can also take 6 week classes for those who enjoy a more structured approach. It is well organized, easy to use and best of all costs nothing.
 I especially love the convenience of being able to stream yoga on my computer where I can do my Down Ward Dog in private. It's also great for those who live in remote places or who can't make a class because of busy schedules.
I knew you could do yoga in many places, by the ocean or a mountain top but the most unusual place I recently saw, was a group doing their Warrior poses in what I consider to be extreme yoga, on their flat boards in the marina on Canandaigua Lake.  I was in awe that they were able to balance themselves on their boards while staying on top of the water, when I struggle to keep my balance on solid ground.
Where ever you choose to do yoga and what ever your level, yoga has health and emotional benefits worth pursuing. Namaste!