Free
Google Chat
Download Google Chat for Windows: Collaborate in real-time, anytime
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A free and secure messaging tool
Feem for Windows - Painless file sharing!
Take part in videoconferences with your buddies on ICQ
Aggregator app for online messaging services
AIM: Free Instant Messaging for Windows Users
Free and anonymous instant messaging service
When social networking meets corporate communication
Server-side software that organizes, manages and controls all of your private IM system.
Exchange encrypted instant messages and files over office LAN, business networks
Old-fashioned and out-dated instant messaging platform