LibraryLookup
Oh man, this is the best bookmarklet/browser hack I've seen in a long time. So you're looking at a book on Amazon.com and you want to see if your local library (remember libraries? free books, music, and movies!) has it ... just click the bookmark and it opens up a window with your local library's catalog. It works! Here's the bookmarklet for my local library (I just dragged the link up to my bookmarks): Arlington Heights Memorial Library.
Well done, Jon ... fantastic.
Source: Jon Udell: LibraryLookup (Build your own bookmarklet)