Buzz 3D VideoChat Plus! 

2 Programs in 1 : VideoChat (1-to-1 chat, Personal Address Book, BuzzCard invite-a-friend, NAT Router / LAN Support and easy setup Wizard) & VideoChat Plus! (High Quality Audio / Video Group Chat, Real-Time Conference Recording & Video email).
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NetChat 

NetChat is a peer-to-peer local network messaging and communications system for Windows which does not require a server to be running for use. It allows you to chat in real-time with other users on a secure and private local network connection.
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ENat for MSN Messenger 

ENat for MSN Messenger makes it possible to talk with anyone using MSN Messenger voice chat or video chat even when behind NATs where attempts to talk using MSN Messenger voice & video chat usually fail. It also enable file transfer when behind NATs.
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