The following sites display information on pop-up books.
The Great Menagerie: The Wonderful World of Pop-up and Movable Books, 1811-1996, The University of North Texas;
The Movable Book Society homepage
Pop Goes the Page
Pop-Up, Peek, Push, Pull... : An Exhibition of Movable Books and Ephemera from the Collection of Geraldine Roberts Lebowitz
The Wonderful World of Pop-up and Animated Books [Wayback machine]
WORLD OF THE CHILD: Two Hundred Years of Children's Books UNIVERSITY OF DELAWARE LIBRARY, Special Collections Department;