FOAFox, discover FOAF profiles in Firefox.
FOAF (the acronym means Friend-of-a-Friend) is a RDF/XML format to describe persons, and his relationships, into the semantic Web. You publish your FOAF profile in your Web page, and you and your friend will go making a semantic social network.
Also, if you link your FOAF in the Web's head, when a user, who have FOAFox installed, could see your FOAF in a friendly HTML-based interface.