After Google with GTalk (~ 180 million users) , now also Facebook (> 400 million users ) has switched its chat protocol to Jabber/XMPP ( pdf introduction). Now you need simply a generic xmpp client (like Adium, iChat, Miranda, Pidgin) and configure Facebook, Gtalk,..
XMPP is now the de facto the Standard protocol for Instant Messaging
We are next to have an Interactive Internet: like emails that can be sent out of a domain, we’ll be able to chat with people outside our domain: with my gmail account I’ll be able to chat with facebook people !!!!!!!!!!!!
See the video “Set-up an Enterprise Instant Messaging server in 180 seconds“