Trillian

Trillian is a free fully featured, stand-alone, skinnable chat client that supports chatting on Windows Live, Facebook, Yahoo, MySpace, AIM, Email, Google Talk, Skype, ICQ, Jabber, IRC, and Bonjour. It also helps manage your social networks such as Facebook and Twitter. Trillian provides capabilities not possible with most original network clients, while supporting standard features such as audio and video chat, file transfers, group chats, buzzing, tabbed chats, tablet-based drawing, message history, plugins, avatars, multiple simultaneous connections to the same network, typing notifications, proxy support, and encrypted messaging.