Identi.ca supports XMPP and FOAF.
Dan Brickley with Libby Miller created the FOAF specification. You’ll enjoy Dan’s article: “Be your own twitter: laconi.ca microblog platform and identi.ca.” He says:
The laconi.ca microblogging platform is as open as you could hope for. That elusive trinity: open source; open standards; and open content.
As rjeffries, I’ve been using the identi.ca microblogging service quite a bit recently. It supports the XMPP (Jabber) protocol, so you can use the Twirl clinet for real-time updates if you like. Identi.ca also supports the Friend of a Friend (FOAF) protocol. You can see my FOAF if you are so inclined.