I'm always interested in seeing the behind the scenes of how anything is done. When I finish a movie, I go straight to the special features and watch all of them (my wife hates it). Watching the special features on the Lord of the Rings trilogy is an event unto itself!
I love storyboards, art of books, sketches of character expressions, concept art, all that crap. They give insight to how the final product was created. It's a good reminder that ALOT of work went into the final product and inspires me to put ALOT of work into anything I do.
These are page thumbnails from Armstrong 1 and 2.