Use the -Y parameter on ssh, or -X on older versions that don't recognize -Y. For example, on machine1, issue the command:
ssh -Y userid@machine2
Any X applications you run on machine2 will then display on your local (machine1) video.
Of course, you must be running an X server on machine1. If machine1 is a Windows system, you must install Cygwin
(if you don't already have an X server installed) and start it's X server before you ssh to machine2.