I haven't read all the previous answers so someone else may have already mentioned these. I like Jessica Valant, who is a PT. I've never seen anyone else on this forum mention her, but I really like her videos. They are not all osteoporosis-specific but many are. I also like Girl with the Pilates Mat who also has many videos geared toward osteoporosis. I've also found many good ones for osteoporosis on Silver Sneakers.