AOL Instant Messenger -AOL instant Messenger (AIM) service is a free online service that has been around for years.  This popular IM program 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 has a lot of new features, including Video IM, Screen Name Linking, AIM Games and Mobile IM.  Always fun and easy to use, the only problem you may encounter with this software is finding a screen name that hasn't already been taken. 

Yahoo Instant Messenger - Yahoo! Messenger is a free instant messaging service that you can use to communicate with other people who also use Yahoo! Messenger. You can see which of your friends are online and communicate with them in real time. Yahoo! Messenger also has great features for Entertainment, Personalization, Productivity and communication.  Using the Yahoo ID system, you will be able to login to your Yahoo Mail, My! Yahoo, Yahoo! Personals, etc. 

MSN Messenger - Use your Email address as your screen name with this popular IM program.  With many of the features included in the other Instant Messenger programs, MSN Messenger allows you to request Remote Support.  This features enables someone to take control of your PC with your permission to help you solve technical concerns.  Get MSN messenger now!

Trillian- If you don't like commitment, try Trillian.  Trillian is a fully featured, stand-alone, skinnable chat client that supports AIM, ICQ, MSN, Yahoo Messenger, and IRC.  It calls itself the Swiss Army Knife of Instant Messaging, and has both a free and Pro version.