Just got back from a two day intensive course with Scott Smalley in NY on orchestration. All I can say is, if you ever have the chance to take Scott's class, do it!!!!! It was one of the best seminars I have ever attended! GREAT STUFF!
I attended Scott's New York session a few years ago with another composer from our studio. "Eureka moments" describes the experience well. In addition to a load of useful orchestration techniques, Scott explained the mediant harmonic relationship in such a simple, useful way that it practically changed the way I approach composing for film.