Empathy - Apps/Empathy - GNOME Wiki!
Wickr - Wickr is a free end-to-end encrypted text, video, picture and voice messenger with full sender...
Psi-IM - Psi-IM is a messaging program that is designed for the XMPP network.
Burn Note - Burn Note is the name of a continuous private messaging utilizing which you can have an ongoing private discussion with your companions or any individual who is at Burn Note.
Gajim - Full featured and easy to use Jabber client
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.