ESDi
Talk to one or more people at the same time via your PC using this intercom application. Designed for your local area network. Talk directly to a particular person or talk to a group. Groups are made up of people working on the same project or in the same department etc.
http://www.enigmasoftwaredevelopments.com/SETUPi.EXE - 160Kb - Download - Screenshot

IMBoss Google Talk Sniffer Monitor
Monitor Google Talk Messenger Conversations on your LAN,query logs,export Html or excel fiel! 'IMBoss Google Talk Sniffer Monitor' is a network visibility tool to capture conversations of a Google Talk chat in your local network. 'IMBoss Google Talk Sniffer Monitor' consists of a well-integrated... It's easy to use, and it will monitor all conversations in your "Local Area Network" without the use of client software installed on the remote computer. ... 'IMBoss Google Talk Sniffer Monitor' can save all logs into database for provides rich-features report and finding system .
http://www.imbosstech.com/download/imbgoogle.exe - 2Mb - Download - Screenshot

MSNTalk
MSNTalk - easy to use replacement for standard WinPopup. Allows to chat in a local network both in the conference mode, and private talks. Does not depend on the installed network protocols (can work in TCP, IPX, etc networks).
http://www.softcomplete.com/download/msntalksetup.exe - 564Kb - Download - Screenshot

Boogy Chat
Boogy Chat is not just a chat for local networks. This chat was and is still being designed with the only objective, namely, to have a pleasure from the talk. Main Options: - Common chat. - Private talk. - Talk to several users simultaneously (group talk). ... - Boogy Chat is intended to talk with pleasure! ... - Operation of the chat without a special program on the server. ... - Audio notices of events. ... - A convenient and simple to use interface; a detailed description of the program. ... You will be informed about incoming messages.
http://www.boogychat.com/download/BCSetup.exe - 1Mb - Download - Screenshot

Combat Pillows
Enter true multiplayer environment on your local network - or play alone - and fight Extremely Aggressive Pillows (EAP) in Combat Pillows. Your objective is simple: make as many kills as you can and stay alive! In the process of doing that, enjoy the stunning graphics and rich sounds made... Use built-in chat to talk to the other players. ... No complicated installation is necessary, just download, double-click and play! ... Open architecture allows many add-on levels and movies.
http://iwannaplay.com/cp/combatpillows.exe - 3Mb - Download - Screenshot

SeaWar
SeaWar is Battleship clone game. You can play against both a computer and a human over a local network or the Internet. You can talk to an opponent during the game by means of embedded chat. The game has nice and intuitive interface with skins support, which you can download from the game site. ... You can easily play the game at your workplace. ... The ESC key quickly hides the program to the tray area. ... Various types of game and 7 levels of complexity give you extraordinary game experience.
http://www.one.com.ua/seawar/download/seawar.exe - 3Mb - Download - Screenshot

OfficeIntercom Communication Software
OfficeIntercom lets you use your computer to speak to others over the internet or your local office computer network. It works as a virtual intercom and feels a little like using a CB radio. To talk to anyone else who has installed OfficeIntercom anywhere in the world, just hold down a key on... It saves your phone bills and, in an office environment, no further cabling will be required to run OfficeIntercom because it uses the existing network. ... For quick questions within a workplace, OfficeIntercom is a much more efficient communication system than dialing telephone calls or typing...
http://www.audiochannel.net/software/oi.zip - 186Kb - Download - Screenshot

SnapTalk
SnapTalk is the cross-platform private chat and file transfer utility for your office. Instantly send messages and files on your local network. More powerful than standard chat, SnapTalk includes full featured archiving and search of transcripts. In addition, SnapTalk includes customizable... It also increases security and productivity because all messages are kept in-house. ... You can be sure that everything in SnapTalk is company business. ... SnapTalk seamlessly connects Mac and Windows computers!
http://www.glassbead.com/download/files/ST_WinInstaller.exe - 10Mb - Download - Screenshot