1)   NetChat 2.6
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.

 2)   IntraMail 2003.01.20
Secure exchange of messages in a local network Intranet (Windows 95, 98, Me, NT, 2000, XP). The mail can be written or read from any PC easily. Every mail-account can be protected by a password. Personal messages are strongly encrypted.

 3)   Invisible Chat 1.22
Invisible Chat is a software for communication by LAN .You can make it "invisible" for prying eyes, when undesirable person is staying behind. You can change transparency, form, color, font and other parameters.