Pidgin is a chat program which lets you log in to accounts on multiple chat networks simultaneously. This means that you can be chatting with friends on Windows Live Messenger, talking to a friend on Google Talk, and talking to your friends on Facebook via XMPP without the need to log into the Facebook website.
Pidgin offers compatibility with many popular networks, including AIM, ICQ, Google Talk, Jabber/XMPP, Windows Live Messenger, Yahoo!, Bonjour, Gadu-Gadu, IRC, Novell GroupWise Messenger, QQ, Lotus Sametime, SILC, SIMPLE, MySpaceIM, and Zephyr. It can support other networks using plugins.
Download: Pidgin 2.6.6
Thanks to Neowin member Rabbai for the heads up!