Psi
Psi is the premiere Instant Messaging application designed for Microsoft Windows, Apple Mac OS X and GNU/Linux. Built upon an open protocol named Jabber, Psi is a fast and lightweight messaging client that utilises the best in open source technologies.
More information about Psi, it's fora, development schedules and mailing lists can be found at http://www.psi-im.org/
Psi Nightly builds
You can, however, try some of our nightly CVS builds for Debian. These
are compiled to be used on Debian Sarge but are confirmed to work on Ubuntu
Hoary as well.
As these builds are created fully automatic, we cannot guarantee their
correctness. This means you can use them at your discretion without any
warranty whatsoever.