Using VNC you can control your desktop from an other computer. In KDE there is a VNC server called krfb. The main disadvantage of this, is that when you move the mouse on the server, it does not move the mouse on the client.

There is another VNC server that works better and can connect to any already running X display. It is called x11vnc. Here is how I use it.

First, invent a password and save it using this command:

x11vnc -storepasswd

Then use the following command to start up the VNC server:

x11vnc -display :0 -xkb -rfbauth .vnc/passwd -auth .Xauthority -shared -http

You can use this command from an SSH session, and you can access the server also using a web browser instead of an VNC client. The built-in web server listens on port 5800 by default. If you prefer to use a VNC client, then xtightvncviewer is a good choice.