If they're on a network, you can either enable xdmcp, as Mark suggests (Edit: looking back, that's not what Mark suggested, but it is another possibility), or, even easier, just log in remotely using ssh and its X11Forwarding option, which is "-X" for OpenSSH. You'll have to enable it on the server, too, in /etc/sshd_config, or wherever your distribution might put that config file.

Anyway, once you get ssh's X11 forwarding working (not really difficult), just log in remotely and all X clients will be sent back to your local display. No need to even get out of your chair.