FOAF (CommunityWiki:FOAF) allows you to keep the data under your control, unlike all the other networking software out there (Orkut, Tribes, Linked In, Rhizome).
Use FOAF-a-matic to create your own.
The WebOfTrust will be important in the future, I believe. (Added in 2023: I was totally wrong!) My public key is available from a keyserver near you.
The following scripts use Oddmuse:wikiupload.
#!/bin/sh wget -O /tmp/foaf.rdf http://www.emacswiki.org/cgi-bin/alex/download/FOAF gnuclient /tmp/foaf.rdf
#!/bin/sh cd /tmp gpg -a --detach-sign foaf.rdf wikiupload -m yes -u AlexSchroeder foaf.rdf http://www.emacswiki.org/cgi-bin/alex/FOAF wikiupload -m yes -u AlexSchroeder foaf.rdf.asc http://www.emacswiki.org/cgi-bin/alex/FoafSignature