Skype for Mac
Skype is a little program for making free calls over the internet to anyone else who also has Skype. It's free and easy to download and use, and works with most computers. Now it also supports video conferencing over the net.
MSN Messenger for Mac
Macintosh users have a combined home and corporate client dubbed Microsoft Messenger for Mac rather than MSN Messenger for home use and Windows Messenger for corporate use. The Macintosh version has far fewer features than its Windows counterpart; though released several months after MSN Messenger 7.0, does not offer voice conversations, webcams, online games, and several other features already introduced and popular with Windows users. Another minor upgrade for Mac was released in March 2006, but it still does not support audio, video, or other extended features.
AIM for Mac
AOL Instant Messenger is World's most popular chatting program. AOL instant Messenger (AIM) service is a free online service that lets you communicate with family, friends and co-workers in real time. Using the AIM Buddy List ® feature you can see when your buddies are online and available to instant message. The newest version of AIM lets you to take instant messaging to the next level! With Video IM, Screen Name Linking, AIM Games and Mobile IM, instant messaging has become more fun than ever! Now new AIM messenger (AIM Triton) contains AOL Explorer built in. New look and layout will defiantly make AIM more popular than ever before. Please note that AIM Triton download contains setup files only.
Adium for Mac
Adium is an instant messaging client for Mac OS X that supports multiple protocols through the libgaim library. It is written using OS X's Cocoa API, and it is released under the open source GNU General Public License. Adium was originally created by a college student named Adam Iser, and the first version, 1.0, was released in September 2001. The next version-originally slated to be called Adium 2.0, but then renamed to Adium-is a complete rewrite of the code of the 1.x series. Its largest improvement was switching to libgaim to add support for IM protocols other than AIM; supported protocols now include ICQ, MSN Messenger, Yahoo! Messenger, and Jabber. Most of the work on libgaim itself is done by the gaim team; the Adium team mostly works on the Adium graphical user interface (GUI).