Trillian

Trillian is the ultimate instant messenger. From one single interface, you can communicate with all the popular instant messengers, including AIM, MSN Messenger, Yahoo Messenger, ICQ, and IRC. And it takes advantage of the unique features of each program, including file transfers and audio chats.

Send text, pictures, audio, video and more... Video and audio calls are directly integrated into Trillian over the Trillian Astra network, not pushed into a third-party web browser solution. Thanks to Tabbed Chat reduce desktop clutter by grouping message windows together with a simple drag and drop. Tabs show the status, avatar, and recently-received messages from each window, and support standard keyboard shortcuts to change between them