NoMachine NX is a Terminal Server and Remote Access solution based on open source technologies. It makes it possible to run any graphical application on any operating system across any network connection as if you were sitting in front of your computer.
Read it at Linux-tip.net
If you'd like to discover how NoMachine's servers work or are configured, give it a try! The following workshop describes the NX Free Edition installation and usage on a Debian 4.0 server.