FreeNX (http://freenx.berlios.de/) is a Terminal Server for Unix & Linux, similar to windows remote desktop \or linux 2xTerminalServer. It is based off the non-free NX (http://www.nomachine.com/index.php). \FreeNX client is only for linux, but NX has free clients for windows (http://www.nomachine.com/download.php)
sudo add-apt-repository ppa:freenx-team
sudo apt-get update
sudo apt-get install freenx
sudo /usr/lib/nx/nxsetup --install