Kopete
- Linux based, KDE specific, it is a flexible and extendable multiple protocol instant messenger.
- http://kopete.kde.org/

Centericq
- A text mode menu and window-driven IM interface that supports the ICQ2000, Yahoo!, AIM, MSN, and IRC protocols and has many other useful features.
- http://thekonst.net/centericq

Pidgin
- An instant messaging client, which can handle multiple protocols, including AIM, ICQ, IRC, MSN, Yahoo!, Jabber, and Gadu-Gadu. [Windows, Unix]
- http://pidgin.im/

Gtkmsn
- A MSN protocol based client. Includes download section and screenshots.
- http://gtkmsn.sourceforge.net/

BigBlueBall.com
- Instant messaging tutorials, reference, news and forums for AIM, MSN, Yahoo, ICQ, Trillian and other products.
- http://www.bigblueball.com/

P2P Messenger .NET
- A secure Instant Messaging client, working by Peer-to-Peer technology. It is fully decentralized and does not require any servers. Supports public-key cryptography. Requires installing .NET-Frameworks.
- http://www.ufasoft.com/p2p/

Winpopup LAN Messenger
- A full-featured server-less instant messenger for Local Area Networks.
- http://www.winpopup-lan-messenger.com

Endogy
- Endogy provides Instant Messaging software and consulting services for the improvement of team workflow.
- http://www.endogy.com

komunikator tlenplus
- An extended Tlen client with emotes,skins, and plugins.
- http://www.tlenplus.webpl.org

Meca Messenger
- Multi protocol Instant messenger with: multimedia integration, skins, SMS capabilities, logs, email viewing and offline messages.
- http://www.meca.com/

WinPopup.com
- Windows popup messenger. Has the ability to transfer emoticons, and links.
- http://www.winpopup.com

Miranda Instant Messenger
- A modular open-source multi-protocol instant messenger for Windows that maintains an extensive database of community developed plug-in's that add functionality.
- http://www.miranda-im.org

OUGO Messenger
- A Windows Messenger.
- http://www.ougo.com

OMS Online Messenger Service, SOAP Webservice
- A webservice for creating one's own messenger client. Included is a webbased version of OMS.
- http://www.myoms.net

EMSN Messenger
- EMSN is a PHP-Messaging System.
- http://stdio.ch

PowWow Messenger
- A multi-functional instant messenger program. Including: Chat, Text to Speech engine, games, guestbook, and whitepages.
- http://www.jazy.net/powwow/

VSL LanToucher
- Instant messaging software solutions for business and home text communications across private networks.
- http://www.vitalsoundlab.com

SimpleAIM
- An open source miniature conosole based AIM client written in pure Java.
- http://simpleaim.sourceforge.net

Trillian
- A chat client for Windows that allows you to simultaneously connect to AIM, ICQ, IRC, MSN and Yahoo! Messenger.
- http://www.trillian.cc/

Easy Message
- Free all in one instant messenger, including support for MSN Messenger, Yahoo Messenger, AOL Messenger, and ICQ Messenger.
- http://www.easymessage.net

Bantu
- Offers a web-based solution to instant messaging that lets you talk to people with the AOL, MSN, YAHOO, and ICQ messangers.
- http://www.bantu.com/

Rediff Bol
- Allows user to chat, check mail, and search the web.
- http://bol.rediff.com/

ActivePager
- An instant messenger for local area networks enabling you to talk in real time to anybody on the same computer network. Offers Answering Machine, and Templates and Blacklist.
- http://www.reymax.com/active_pager.html

BattleCom
- A program that allows you to talk instead of type, a new way of chatting.
- http://www.battlecom.fw.nu

Integrity Messenger
- Messaging service that provides instant contact with Internet users, language filtered and family safe.
- http://www.integritymessenger.com