Yahoo Messenger
- Official client. Available for Mac OS 9 and X.
- http://messenger.yahoo.com/mac.php

iChat AV
- Apple's text and video messaging program for Mac OSX.
- http://www.apple.com/macosx/features/ichat/

QuickPopUp
- Allows users to exchange instant messages with other users on a LAN and across multiple operating systems.
- http://www.quickpopup.com/

PalaceChat
- Unique visual instant messaging client. User assumes an avatar and moves around palace "rooms" interacting with other users.
- http://ee.fastpalaces.com/

MSN Messenger Service
- Official MSN chatting client.
- http://www.microsoft.com/mac/default.aspx?pid=msnmessenger

ICQ
- Official ICQ client for Mac OS 9 and X.
- http://www.icq.com/

Nitro
- Jabber client for Mac OS 10.3 or later.
- http://nitro.jabberstudio.org/

JabberFoX
- An open source instant messaging system fully based on XML.
- http://jabberfox.sourceforge.net/

Adium X
- A free multi-protocol instant messaging client for Mac OS X, released under the GNU GPL. Includes program download, screenshots, project news, and development information.
- http://adiumx.com/

AOL Instant Messenger
- Official AOL chat client for the AIM protocol.
- http://www.aim.com/get_aim/mac/latest_macosx.adp