Trillian

Trillian is a fully featured, stand-alone, skinnable chat client that supports AIM, ICQ, MSN, Yahoo Messenger, and IRC. It provides capabilities not possible with original network clients, while supporting standard features such as audio chat, file transfers, group chats, chat rooms, buddy icons, multiple simultaneous connections to the same network, server-side contact importing, typing notification, direct connection (AIM), proxy support, encrypted messaging (AIM/ICQ), SMS support, and privacy settings.

Without stealing your home page and with no other included software, pop-ups, or spyware, Trillian provides unique functionality such as contact message history, a powerful skinning language, tabbed messaging, global status changes (set all networks away at once), Instant Lookup (automatic Wikipedia integration), contact alerts, an advanced automation system to trigger events based on anything happening in the client, docking, hundreds of emoticons, emotisounds, shell extensions for file transfers, and systray notifications.

Features:
>Improved speed
>Many IRC enhancements
>Better Yahoo file transfers
>Identities (per section Biography/Icons)
>Biography (AIM Profiles)
>Universal Plug-and-Play (UPnP)
>Undo in edit area
>Orphaned contacts (no more merging)
>On the fly link/emoticons
>Font face support in IMs
>Bug fixes

Can manage connections ,skins,plugins,message windows,contact list,notifications,text conversations and history.Sort users by status,service or alphabetically.Hide or show identity panel.The design represent a plus,is light and modern.