gaim

Multi-Protocol and Multi-Platform IM client. Allows you to be logged into the following IM services: Aim MSN IRC ICQ Yahoo Jabber Gadu-Gadu Groupwise Napster Zepphyr Is tab based, so you have all your conversations in one window, and can easily switch between them by ctrl+tab or simply clicking the tab. Supports plugin's which can easily be installed and downloaded from sourceforge. Has many more features designed to make IM'ing much faster and more simple to do.