Yahoo! Messenger allows you to quickly exchange messages with your online friends. Unlike e-mail, instant messages appear as soon they're sent. BBy downloading the application to your computer, you can send instant messages. Other features include voice chat, file transfer, mail and stock quote alerts, sports scores, news, and much more.
Viber for Windows lets you send free messages and make free calls to other Viber users, on any device and network, in any country! Viber syncs your contacts, messages and call history with your mobile device.
TeamTalk 4 is a conferencing system which enables a group of people to collaborate and share information. Every member of a group can communicate with other members in real time using both audio and video. All that is needed is a microphone and a web camera.