The Making of Star Wars: The Empire Strikes Back, a book by J.W. Rinzler, is now available on Amazon. Wired.com has a review and a neat list of 10 things you probably didn't know about The Empire Strikes Back. Did you know that Yoda was originally named Buffy (as in vampire slayer), Vader wasn't Luke's father at first ("Luke, I am...not your father") and Miss Piggy had a surprise cameo in one rehearsal (wish they had caught that on camera!).
Vanity Fair has a selection of rare, behind the scenes photos from the book which is worth a look for any Star Wars fan.