In-game return to desktop (10.4.4)?

Does anyone know how to return to the desktop while a game is running in full screen (e.g Diablo II)? I hear emails coming through sometimes while I'm playing and I want to be able to quickly look at them but keep the game running. Thanks in advance.

In Halo (fullscreen), I can hit F11 and go back to the desktop.

I think it depends on what game you have though.

Hitting F11 moves all windows in OS X to the side and allows you access to the desktop.

Thanks a bunch!

edit: Actually that did not work for D2. Command>M = window mode works. Thanks again though.