For a recent project markus and me just coded some scripts and a flash-movie for presenting a portal.
The idea is show the construction page when visiting http://yourportal.com until you “publish” the portal.
The flashmovie counts down from 9 to 0 and redirects to the startpage (there is also an undo button for setting the portal offline, in case you pressed too early)

These are 2 screenshots of the countdown and the menu.
(the countdown numbers are fading in and out, it really looks much better than on the screenshot)

Feel free to modify and use this stuff for presenting you own portal.

Note: Publishing is not done by changing workflow states of objects so this is no secure way to “hide” your portal content from searchbots or nosy people. There is just a index_html script that redirects to http://yourportal.com/construction or to http://yourportal.com/view depending of the current state of your portal (given by a property on the plonesite) for more technical details please refer to the readme.