I have an educational fly fishing guide business, Fly Fishing Traditions, and I teach beginning fly casting using the "Orvis Method". It's really good investment for a beginning fly fisher. The Orvis casting video, "The Orvis Guide to Fly Casting". runs $25 and it worth it. It gets you started with good fundamentals right from the start.
Fly Casting Video / The Orvis Guide to Fly Casting DVD -- Orvis