I like to suggest vnc4server, which is easy to use:
Virtual network computing server software VNC stands for Virtual Network Computing. It is, in essence, a remote display system which allows you to view a computing `desktop' environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures.
This is nice, if the user on the other side shall see, what you're doing on his machine.
But the normal Xserver is - surprise - a server.
allows you to connect to a foreign host, and start a graphical program on the remote machine, which is displayed on your local machine (not visible on the remote machines monitor). You might have to fiddle around with the Xauth, and I can't tell you what to do exactly - it's too long ago I used it.