People probably wonder why I get books for real media when I don't do anything other than Photoshop work. The answer is very simple, I use real media techniques in Photoshop. If you ask me how that's possible, then you don't know Photoshop. If you tell me to use Painter, I tell you Photoshop is better for me. I have Painter, now consider that nothing I make is in Painter.
Anyway I picked up one of these books. It just came in today. I haven't had time to read it, but I've been looking over the techniques. I think it would come in handy for a lot of budding artists. Show's a lot of good "how to's" for rendering animal fur, feathers and scales with various media. This probably wouldn't be very good for any advanced artists reading this, but you could always take a peek at your local bookstore.
Drawing and Painting Animals: Problems and Solutions by Trudy Friend