Web Based Instant Messengers

Sometimes the web based messengers can be very useful - especially in work, school or somewhere else where installation of new software is forbidden (for example, look at that comment).
Many of them are not as comfortable as the regular instant messaging applications but they are working.

Here are some messengers for the most popular instant messaging protocols:

ICQ - ICQ2Go
http://www.icq.com/icq2go/
There are both Flash-based and Java-based versions.
Here are some screenshots from the Flash-based ICQ2Go. With Mozilla Firefox it looks strange sometimes but it works.
Screenshots: 1 | 2

AOL IM - AIM Express
http://www.aim.com/get_aim/express/aim_expr.adp
AIM Express lets you send instant messages directly from a Web browser, such as Netscape Navigator or Microsoft Internet Explorer, to anyone who has registered for AIM or who uses the America Online service. AIM Express respects your privacy and, best of all, its FREE. To use AIM Express, you must be a registered AIM user or subscribe to America Online.
I tried to use it but I always see this error. Maybe the problem is with my browser or its extensions. Here is a screenshot from the official website.

Jabber - JWChat.org
http://jwchat.org
It uses only HTML and Javascript. Looks interesting. Unfortunatelly, when I tried to login with my Google Talk account, Mozilla Firefox became "Non-responding". I'll try with another browser later.

MSN - MSN Web messenger
http://webmessenger.msn.com
MSN Web Messenger lets you talk online and in real-time with friends and family using just a web browser! Use it on any shared computer - at school, at work, at a friend's house or anywhere you can't install the MSN Messenger software.
Don't forget to allow the site in you popup blocker if you have one.
Screenshots: 1 | 2

MSN - Clientless Conversations
http://www.clientless.net/
This service allows you to use the popular MSN Messenger service with only a browser. No downloads required!
Do you need to chat at work, at home, at university, behind a firewall, or on a kiosk? Clientless Conversations is a free simplistic Web Based MSN Messenger Client which allows you to chat anywhere!

MSN - MSN2Go
http://msn2go.com
MSN2Go is a web-based MSN client or web-based MSN Messenger client that enables you to access the MSN Messenger network at work, school, or anywhere else.

I couldn't find a web-based messenger made by Yahoo. But e-Messenger supports YIM.

All-In-One - E-Messenger
http://e-messenger.net
e-Messenger is a web application that enables you to chat with your MSN, AOL and Yahoo buddies without having to install any program or Java applet. All you need is a JavaScript enabled browser and you're set to go and use e-Messenger. Even if you're behind a firewall.

All-In-One - Instant-Messenger.info
http://www.instant-messenger.info/
Here you can use MSN, AOL and Yahoo. It also doesn't use Java or Flash.

All-In-One - Meebo
http://www.meebo.com
Meebo is a really interesting all-in-one instant messaging client. It is based on Ajax and the interface is very comfortable. It doesn't have some special functions but it works great as a web-based messenger. Supported protocols are: AIM, ICQ, Yahoo, Jabber, Google Talk, MSN.
Thanks to that visitor for the link about Meebo :-)

Goowy
http://www.goowy.com
Goowy is a web-based application offering Free Web Email service that enables you instant messaging, chat, file sharing and much more with your buddies from AOL, MSN, Yahoo and ICQ.