Meebo – the web-based IM on any network or site 

Meebo is an instant messaging solution. Instead of asking you to install a client on your computer, manage all your instant messages through Meebo’s website (even if they have a small system tray notifier available for Windows users). Registration is optional if you use a single service such as AIM, Yahoo! Messenger, Google Talk or MSN Messenger, simply use its power for the service to connect to it by Meebo. If you want to build a more sophisticated world that newspapers in several services at once, you’ll need to open a free account, Meebo. A bonus for those behind a corporate firewall, assuming that your firewall is not blocking the site of Meebo is that you can use to secure Web sites (with https: / / name), can be connected to all your favorite chat services.
Meebo is here.