ChatSc.com

QuickPopUp
Allows users to exchange instant messages with other users on a LAN and across multiple operating systems.
www.quickpopup.com/

PKIChat Secure Instant Messaging
Secure instant messaging using auto generated public/private key pairs.
www.pkichat.com/

Jephyr Instant Messaging System
Protocol specification for client-server instant messaging with a Java implementation.
hugh-kennedy.chicago.il.us/

Arliweb Messaging Platform
Arliweb XMP is an XML and web services based messaging service and software application.
www.arliweb.com/

A&M Instant Messenger
Provides instant messenger system to use in Internet and corporate LAN/WAN.
www.amsoftwaredesign.com/

Hubbub Instant Messenger & Presence Application
Hubbub is an Instant Messenger that makes use of various song snippets to give you an awareness of your friends and colleagues.
www.hubbubme.com/

AOL Instant Messenger
Official AOL chat client for the AIM protocol.
www.aim.com/

JabberFoX
A Jabber client for Mac OS X. An open source instant messaging system fully based on XML.
jabberfox.sourceforge.net/

AIMMachine.com Offline Messaging
Service allowing you to message users that are currently offline.
www.aimmachine.com/

Nitro
Jabber client for Mac OS X.3 or later.
nitro.jabberstudio.org/