Pidgin is a free multi-protocol multi-platform instant messaging client. Prior to
Pidgin I was a die-hard Trillian user. While it’s true that Trillian "Astra" will be
available soon enough, the existing v3.1.8 client is old, ugly and is purposely
limited in the "basic" version (the "pro" version costs $25).
Pidgin on the other
hand is free and does everything without costing a dime.