Any one suggest a free alternative to teamviewer?

VNC

Empathy + Jabber is the only I can think of.

To my best knowledge there is no comparable alternative to something like Teamviewer or Citrix GotoMeeting. As least not with such a simplicity behind a router.

The german computer magazine C't once did a package based on VNC and several other tools to enable users to do remote administration without special setup but AFAIK this was limited to Windows clients only.

I found:

http://jrdesktop.sourceforge.net/index.php

http://www.kde.org/applications/internet/krdc/

But I do not know whether they are suitable to you.

@Relevation:
krdc is a client for the VNC and M$ RDP protocols. This requires a corresponding server on the machine you want to connect to. For jrdesktop I guess it boils down to the old problem -> you have to configure the router of the person you want to connect to.

We wouldn't have a problem setting up a server for this purpose. The thing is there doesn't seem to be any software which uses a server to avoid the router configuration to begin with.