Similarly you can check out freenx.berlios.de, same principle.  FreeNX server
is free (http://freenx.berlios.de/download.php), and NoMachine is providing
free distribution of their client (http://www.nomachine.com/download.php).  I
have not yet tried it myself, but have been reading about it.

Dan W.

> |OK, this is what I am currently doing using "nohup". However, if X is not gone (I am 
> |talking about a simple log out and return to the login screen), is it possible to keep an 
> |X application running in the background?

> What you can do, however, is start a VNC server, [...]
> like an X session, but is not associated with a physical
> display the way X is.  You can connect and disconnect
> with a VNC client, and the server and X clients keep
> running even if you aren't connected with the VNC client.