Here's a substitue for pop-up folders. It works best with Finder windows, but can be applied for others.Take a window, resize it to a small size but so that you can still see the name of the window, and drag it to the bottom on the screen (should only see the title bar). Now hitting zoom will reveal the window in full. Hitting zoom again will return the window to the bottom of the screen. This is easier to use when the dock is is located on the side of the screen. Enjoy.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2001081821325341