This link shows how to enable an Ubuntu desktop such that a vncviewer can control it.
Note: I used a TightVNC viewer on an XP box. If you put the viewer into fullscreen, you need CTRL-ALT + SHIFT-F to get you out.
This Blog is primarily intended to be a notes-to-self kind of thing. The information contained here is guaranteed to range anywhere from correct to wildly wrong. Use at your own risk. YMMV.