Select bibliography:
Jim Henson: The Works - The Art, the Magic, the Imagination by Christopher Finch (I highly recommend this book)
It's Not Easy Being Green: And Other Things to Consider by Jim Henson and The Muppets And Friends
The Story of Jim Henson by Stephanie St. Pierre

Special thanks to Kat Boucher for the interview and Nick Bachman for loaning his Muppet DVDs.