Adium X
Freeware multiple instant messaging client uses libgaim (the core of gaim) to connect to multiple protocols.
ChitChat
Open source client for Yahoo! Chat enables users to communicate with others over the network.
iChatAV
Features Apple's IM and videoconferencing software, which shipped with the latest versions of Mac OS X.
ICQ
ICQ now brings AOL connectivity to Mac OS X.
Mac Messenger
Freeware version of MSN Messenger offers a native look and feel for Mac OS 9 and X.
MSN Messenger
Official site from Microsoft Features MSN's IM client.
QuickPopup
Delivers cross-platform instant messaging across local networks. Works with Mac OS 9, X and Linux.
Yahoo! Messenger for Mac
Instant messenger program allows users to share live video and works with many mobile phone services.