Empathy - Apps/Empathy - GNOME Wiki!
OpenBoard - The OpenBoard software is an interactive white board software.
Psi-IM - Psi-IM is a messaging program that is designed for the XMPP network.
Conceptboard - Instant Whiteboards for Teams & Projects
Gajim - Full featured and easy to use Jabber client
Scribblar - Scribblar is a free online collaboration tool that is perfect for online tutoring.