del.izzy is a free service that lets you search through your del.icio.us bookmarks. Wait a second, doesn't del.icio.us already let me do that? What's different about del.izzy? del.icio.us is a great service, but when you search through your bookmarks, you are only searching through tags, titles and descriptions, not the page content.
tagthe.net then returns a set of tags based on the textual content you specified. The service is mainly designed for developers, building applications that make use of tagging.
turns search results form google, del.icio.us, amazon, yahoo, etc into live running slideshow of websites that are "live" and browsable while the show is running.
Enter what you're reading or your whole library—it's an easy, library-quality catalog. LibraryThing also connects you with people who read the same things.
B. Krause, R. Jäschke, A. Hotho, and G. Stumme. HT '08: Proceedings of the Nineteenth ACM Conference on Hypertext and Hypermedia, page 157-166. New York, NY, USA, ACM, (2008)