I attended Steve Salkin's workshop on shoulders this past Sunday at Big Island Yoga Center and really enjoyed it. We went through a long list of stretches and techniques to address the muscles in and around the shoulder girdle. If you'd like to receive notice of his next class in Kona, sign up for notices through the BIYC website.
One of the things that has always caught my eye there, is the collection of books on yoga that are for sale. It has to be the best on the island. They have always maintained a wide selection, even better than what Borders used to carry.
A good time to go take a look would either be a few minutes before or after a class. Check their schedule and maybe you'll find a class or two. There's even a free class the first Sunday of every month.