Meerkat RSS feed – the javascript flavour is very cool.
http://www.oreillynet.com/pub/a/rss/2000/05/09/meerkat_api.html

Awesome use of javascript bookmarklets to search for books from amazon in your local library.

http://weblog.infoworld.com/udell/stories/2002/12/11/librarylookup.html