I love yoga; it's simple, low-impact, and great for mental health too. I've been doing it for several years now with a course book from the American Yoga Association. I recently started alternating with pilates, so I get a better mix of flexibility and core/strength training. My New Year's resolution this year is to get up early enough every weekday so I can work out before breakfast, because if I don't do it first thing in the day, it just doesn't get done.