The “Friend of a friend” project is pretty self-evident (which is a good thing). They have a format and are encouraging people to create FOAF-formatted data (mine is here) but they haven’t quite got to the point of implementing distribution and search functions.

A search engine is the obvious function for the data, though none seems to be around yet. It is early in the project at the moment. Also, that search engine really should provide it’s data as a web service.