Trillian IM

Trillian is an IM client, which currently supports AOL IM, ICQ, MSN
Messenger, IRC, and Yahoo! Messenger. It's just over a year old and after
using it for a week it feels more stable than any Jabber client I've used
and worth the download if you need to cross-IM with people. (sorry dave, no
mac client ;-)
http://www.trillian.cc/