LibX Public Library Edition is a Firefox extension that provides direct access to your public library resources. It features:
Toolbar & right-click context menu: Search your public library's web catalog directly from the LibX toolbar or using the right-click context menu.
Support for embedded cues: LibX places cues in web pages you visit if your library has resources related to that page. Whenever you see the cue, click on the link to look at what your library has to offer. For instance, book pages at Amazon or Barnes & Noble will contain cues that link to the book's entry in the web catalog. Cues are displayed at Google, Yahoo! Search, the NY Times Book Review, and other pages.
Support for xISBN: A book title can have different ISBNs for the paperback, the hardcover, even for different editions. LibX supports OCLC's xISBN service: you can find a book, given an ISBN, even if your library holds this book under a different ISBN.