The Dailey Method (and it's competitor The Bar Method) are strength and conditioning studios that use ballet barre work, pilates, and other core conditioning methods to strengthen and lengthen...
It is really amazing... and HARD!! Go to either website (www.thedaileymethod.com or www.barmethod.com) to get more info and to see if it's in your area yet.
I have done both and like Dailey better because they are better at modifying exercises for my bad knees.
I have been working out like crazy for the past months by myself -- cardio training, weight training, free weights, ab classes, pilates, Zumba, etc. and this is the very first day that I've been this sore -- after just one class. It feels great!!!