Tagging

43 Things - What do you want to do?

Tagging is effectively a human version of the section on shopping sites where they say 'people who bought Snoop Dogg also bought The Kills' or whatever. Except that tagging relates people by their interests.
Currently making waves in this area is 43 things , a site owned by/funded by Amazon.
One you join, you list your goals in life. It then allows you to look up who has the same goals as you. Pretty pointless if what you want to do is buy a new hat, but if you want to visit Japan, or do something political you can easily find people who are likeminded. You can also look for aims related to yours, for inspiration.
It's a neat idea, and the site allows you to see a Zeitgeist of what the most popular aims are that day.
It's obviously very much in it's infancy (10,000 registered users worldwide) - but the potential in terms of creating a global community (or, arguably, re-claimin the internet for sad geeks) is enormous.