Carol's pick:
Though I found no medical research on yoga and scoliosis, quite compelling information comes from Elise Browning-Miller, who has used yoga for 30 years for her own scoliosis. Elise was diagnosed when she was 15 with a 49 degree right thoracic curve and compensating left lumbar curve. In 2006, she said that her scoliosis had been reduced to some number of degrees "in the 30s." 

Carol trained with Elise in Dallas, Texas during the fall of 2006.

You can see Miller's web site at:
http://www.yogaforscoliosis.com/elise.html