Part One, Part Two, Part Three.
An Atlas Of Animal Anatomy For Artists is made up almost entirely of anatomical diagrams and hardly any text at all, save the obligatory labels to help identify what you're looking at. There isn't much here to explain how all this anatomy works - which is where the Calderon book comes in (see previous post). Therefore, I recommend using these two books to compliment each other.
This book is fundamentally concerned with anatomical diagrams. Most of these are reprints of Ellenberger's plates. The detail is eerily photorealistic and the amount of information is nearly obsessive:
Dover has a few other AA4A books available in it's catalogue and perhaps I'll collect a few more later on. I remember the Ken Hultgren book from college but never got a copy for myself and the fact that Charles Knight wrote an AA4A book intrigues me. If anyone was ever going to cover non-mammals...
Speaking of, aside from Gregory S. Paul's Predatory Dinosaurs of the World (which I keep cheerleading for and is available at Amazon for just over a dollar so what are you waiting for) I can recommend the following online resources for people who like drawing animals other than humans / dogs / horses:
Skullsite - Page with a wide variety of avian skeletons and nearly every genus represented as a skull. It makes Goldfinger's chicken look downright embarrassing.
University of Puget Sound's Bird Wing Database - Good as a reference for color and markings, particularly the underwings (which tend to be a lot less interesting than you'd think).
Digimorph - Stupid name (it sounds like a terrible action figure line). Amazing site. Gives you the ability to look at every imaginable vertebrate skull in 3-D. There are also several whole skeletons and the site remembers that invertebrates are animals too.
Gaping Maws - This one's more just for fun, but it's a surprisingly good source for photo reference.
Whew... now what can I blog about?