VNC it is ok , but i have a problem using that by my house.
I got optical-fiber connection (isp : Fastweb Italy) and it doesn't support Dynamic DNS.
So from the outside i can't reach my home-PC.
So i think that a Linux (& Mac) Client coul be apreciated a lot !!!
i understand the connection doesnt support dynamic dns but that is really a small problem i think.
once you have full access to the internet that is the main thing.
im sure if all came to all you could write a script to write text somewhere online.
doing this you could set it to write your current ip if the ip in the text was different for example.
then knowing the ip you could connect to a vnc server running on a computer at the ip.
that would be a very basic but unautomated way of connecting.
other methods would be to use vnc with a repeater they call it.
ultravnc can do this sort of connection.
echovnc also does this and even with a free repeater or 'echoserver'.
you connect to the repeater or echoserver and through it can establish a link to the computer you want to control regardless of any firewall or even proxy so long as the proxy allows basic web browsing.