A real find
As a librarian and a Googler, I love the "Find it in a library" links we've added to many -- but not yet all -- of the titles in Google Book Search. While we work on getting these links rolled out for the rest of the books, at least one user has taken matters into his own hands: "Superpatron" Edward Vielmetti has written a Greasemonkey script for Firefox that enables him to see which books are available at his local library.
Since Google Book Search is all about helping you discover and locate books you never knew existed, it's especially gratifying to see people like Ed embracing and extending this mission.