Psi (instant Messaging Client)
Psi is a GPL instant messaging client for the XMPP protocol (including such services as Google Talk) which uses the Qt toolkit. It runs on Linux (and other Unix-like operating systems), Windows and Mac OS X. Previous versions also supported eComStation.
Ready-to-install deb and RPM packages are available for many Linux distributions. Successful ports of Psi were reported for Haiku, FreeBSD and Sun Solaris operating systems.
Due to Psi's free/open-source nature, several forks have appeared, which occasionally contain features that may appear in future official Psi versions. These official and unofficial builds are documented on their external wiki page.
Read more about Psi (instant Messaging Client): Mission Statement, Features, History