You will find here a list of the Jabber client currently available in Debian.
This is far from an exhaustive list, feel free to improve it.
based on GTK libraries
[Depkg:pidgin] (previously named gaim)
[gajim]
based on Qt librairies
[Psi]
Kde Component
[kopete]
text-mode client (console client)
See also:
[http://www.jabber.org/clients wider list of Jabber clients]