Best free instant messaging programs: Yahoo Messenger, AOL Messenger, Windows Live, ICQ and much more!

• Paltalk Messenger
  Paltalk Messenger allows you to see, hear, share files, and chat with anyone, anywhere in the world--all for free. Paltalk operates with AIM, Yahoo, and ICQ, so you can chat with all your buddies using a single program. Paltalk boasts an improved user interface and supports a new x-Treme service level with crystal clear, TV-like video speed, and unlimited video windows.
  
  
• Yahoo! Messenger
  Yahoo Messenger is a free service that allows you to see when friends come online and to send them instant messages. It also can alert you to new e-mail in your Yahoo Mail or Yahoo Personals accounts, or when you have upcoming events recorded in your Yahoo Calendar.
  
  
• GoToMeeting
  GoToMeeting is an online meeting solution. Now it's even easier and more affordable to conduct on-the-fly or scheduled Web-based presentations, product demos, training and collaboration--in real time.
  
  
• AOL Instant Messenger
  You don't have to be an America Online member to experience the immediate cross-Internet communication made possible by AOL Instant Messenger. This program allows Internet users to communicate via private, personalized text messages, and indicates when friends, family members, and business colleagues are online.
  
  
• Windows Live Messenger
  Windows Live Messenger is the next-generation MSN Messenger. It has everything you already love about Messenger—your contact list, emoticons, and instant access to your friends via text, voice, and video—plus new ways to connect and share photos and documents effortlessly. As always, it's free to download Messenger and use most of its features.
  
  
• ICQ 5.1
  ¿The ICQ 5.1 version includes all of the essential communication features such as messaging with the ability to save your chat history, file transfer, sending SMS messages (in selected countries), Voice & Video chats, and an extensive directory search for meeting new people.
  
  
• Trillian
  Trillian is a fully featured, stand-alone, skinnable chat client that supports AIM, ICQ, MSN, Yahoo Messenger, and IRC. It provides capabilities not possible with original network clients, while supporting standard features such as audio chat, file transfers, group chats, chat rooms, buddy icons, multiple simultaneous connections to the same network, server-side contact importing, typing notification, direct connection (AIM), proxy support, encrypted messaging (AIM/ICQ), SMS support, and privacy settings.
  
  
• aMSN
  aMSN is a free open source MSN Messenger clone, with features such as: Offline Messaging, Voice Clips, Display pictures, Custom emoticons, Multi-language support (around 40 languages currently supported), Webcam support, Sign in to more than one account at once, Full-speed File transfers, Group support, Normal, and animated emoticons with sounds, Chat logs, Timestamping, Event alarms, Conferencing support, Tabbed chat windows...