USC's "It's All in the Cards" feature is a Flash widget that celebrates a different card-catalog card every day. I remember the first time I was exposed to my school library's subject index and practically falling over at the thought that there was a way to find all the books in the school (which I assumed were all the books in the world) on any subject that mattered to me. I could look at these things all day.
Maybe I should find a surplus mountain of these things and tile a room with them.
(via Resource Shelf)