This seems to be so obvious and simple but I can't see any quick way to achieve it in Lucid. Because Nautilus does not appear in a menu there seems to be no obvious way of right-clicking and showing it on the panel.
Let's hope I understood the question correctly. You're on Lucid and want a Nautilus launcher on the top panel ? Then go to Menu->Places->Nautilus, click and slide to the panel. You can also create the launcher (right-click on panel I believe) and set the command to "nautilus" or "nautilus /path/to/my/folder"