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

Home Page - http://www.trillian.im/