I often find myself in pop-ups that have no address bars. Safari has an awkward shortcut to invoke the address bar (command+shift+\), but I discovered that the Google shortcut on the edit menu accomplishes the same thing, and is a more natural Option+Command+F. To test this, go to http://www.mac.com and click on the "Help" link just below the Quicktime tab. This results in a classic no-address-bar popup window that you can use to test the shortcut.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040520154153166