mIRC - mIRC: Internet Relay Chat client
Empathy - Apps/Empathy - GNOME Wiki!
HexChat - HexChat is a fork of XChat with bug fixes and new features.
Psi-IM - Psi-IM is a messaging program that is designed for the XMPP network.
Kiwi IRC - A hand-crafted IRC client that you can enjoy. Designed to be used easily and freely.
Gajim - Full featured and easy to use Jabber client