Code4Libers may be interested in something I just released on
LibraryThing. It's called "CoverGuess," and it's a sort of like Google
Labeler for book covers. It turns tagging covers into a competitive
game.

As with much of what we do, the data will be released as Creative
Commons Attribution Non-Commercial. So, with luck and a lot of
LibraryThing community involvement, we may finally have a solution for
the eternal question: "Have you got that book, the one that's blue and
I think it has a girl on it?"

Blog post:
http://www.librarything.com/blog/2010/03/coverguess-game-that-helps-people-find.php

Tim

-- 
Check out my library at http://www.librarything.com/profile/timspalding