T11M

Adium is an outstanding application.  Unfortunately it is currently Mac only.  However, for you Mac users, if you haven’t downloaded Adium you need to right now.  It is the only chat application to support multiple chat protocols including AIM, MobileMe, Google Talk, IRQ, IRC, Twitter, Facebook, and a number of others.  At any one moment I am logged in to 6 different chat protocols and am able to communicate with my contacts on each of them from a single client.  The user interface for Adium is very efficient and user friendly, allowing for quick chatting with multiple contacts.  Adium is also extensible with plugins, emoticon packs, and scripts.  In my opinion Adium is the casual users perfect client and the power users dream.  Check it out here.