Meebo is a web based IM that lets you log into your IM networks from any computer with a browser and internet connection with no firewall issues. It employs technologies (like AJAX) to make it act more like a desktop application, which dramatically improves usability. Many users enjoy the benefits of a native DHTML application, as it does not consume as many system resources as a Java applet (such as ICQ2Go or Yahoo Web Messenger).
Meebome (right) is an embedded chat window for your website/blog -
place the code (available at Meebome) and you're done. This requires at least version 7 of Flash, so download this before pasting the code.