FreeNx (see http://freenx.berlios.de/BrokenLink ) is a free client which can be installed in a Linux system. When installed it can be accessed from a server for NX such as NoMachine. This provides an alternative way of linking computers, which can be compared to VNC (VirtualNetworkComputing).
One use of this is to connect between the host computer and the Linux system being run using CoLinux.
The main web site has disappeared although linked from several locations. The files are available from here: