Greasemonkey is a Firefox extension which lets you to add scripts to any web page to change its behavior. This Library search script will place a link in the Amazon.com interface letting you know if a book is available or not at the UIUC Library.
This script will turn this:
into this:

When you click on the link a new browser window will be opened and a search for that book will be performed in the online catalog. Note, an ISBN search is being done so only this edition of the book is being searched for.