Pidgin, the universal chat freeware
Pidgin is a another chat program that allows you to log in to account several providers at the same chat networks. This means you can chat with friends on MSN, talking to friends on Google Talk, and joked in Yahoo chat rooms at the same time.
Pidgin runs on Windows systems, Linux and other UNIX operating systems. Plidgin also compatible with the chat networks: AIM, ICQ, Google Talk, Jabber / XMPP, MSN Messenger, Yahoo!, Bonjour, Gadu-Gadu, IRC, Novell GroupWise Messenger, QQ, Lotus Sametime, SILC, SIMPLE, MySpaceIM, and Zephyr. Not enough? You can add many more by adding plugins.
Pidgin also supports many chat feature, such as file transfer, away messages, buddy icons, custom smiles, and notification, and many other plugins outside of standard features.

Link download: http://www.pidgin.im/download/