Auch das noch:
Search on Spock to find your friends, old acquaintances, your favorite celebrities, or people you would like to meet. With Spock you can discover people by searching for their name, or by using descriptive tags. For example if you type in "NFL Quarterback" into the search box, Spock will pull back a list of people who play quarterback in the National Football League.
New Ajax social bookmark URL(you can see with what tags one have bookmarked you) and tag search. Says it will be adding more social bookmarking query services almost daily.
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)