I've been doing yoga for about 2 years now and is a great non-impact way to tone your body. The place I belong to also has Pilates, Core, Hatha, Hot Yoga and even a Spin class that I go to all the time. While many instructors vary, there are some with a strong spiritual bent in the way they instruct but you can disregard that and just focus on the physicality that yoga encourages. I am not a spiritual person but do enjoy the calming effect yoga has on me. I also find that people you meet there are so much more grounded than those you would meet at a gym, especially in the weight room ;)
I had to stop playing hockey (breaks my heart) due to knee injuries and between cycling and yoga I have found a way to keep me active with out any impact on the slowly aging body.
Cheers.