Adium 1.4.2 - Popular instant messenger client, supports multiple services.. (Free): Adium is a fast and free instant messaging client which supports AIM, ICQ, Jabber, MSN, Yahoo!, Google Talk, Yahoo! Japan, Bonjour, Gadu-Gadu, QQ, Novell Groupwise, SIP/SIMPLE (Text), and Lotus Sametime. Adium supports beautiful WebKit message display, tabbed messaging, encrypted chat, file transfer, and more. Give it a try; you won't look back.
That's true: it's what I use.