Adium, a fast and free instant messaging program, supports AIM, ICQ (Jabber), Yahoo!, Google Talk, Yahoo! Japan, Bonjour and Gadu-Gadu. Novell Groupwise, SIP/SIMPLE Text, and Lotus Sametime. Adium supports beautiful WebKit message displays, tabbed messaging and encrypted chat as well as file transfer and file transfer. It's worth a try.
Adium is currently translated into