Well, it took them long enough. Facebook Chat now uses XMPP technology.

XMPP (Extensible Messaging and Presence Protocol) is an open-standard messaging protocol, used by many different internet messaging services and many different programs. In other words, you now can chat via Facebook with all of your friends contacts on a separate internet messaging program, without being forced to browse their website.

For your chat program, I personally use and recommend Pidgin. Pidgin is a free, open-source chat program, which works on multiple operating systems and with multiple chat networks. You can set it up to work with AIM, ICQ, Google Talk, Yahoo Messenger, Windows Live (MSN) Messenger, and more.

And now Pidgin works with Facebook Chat also. Instructions for setting up Pidgin for Facebook Chat can be found here.

Enjoy.