<a href="http://xmlns.com/foaf/0.1/">FOAF</a>, or Friend of a Friend, is an RDF syntax for describing yourself and who you know on the web.
There's a tool that'll generate tags for you <a href="http://www.ldodds.com/foaf/foaf-a-matic.html">here</a>...
Thought some people would like to know about this now rather than later... it's kind of exploding.