Comment 24 for bug 681348

OK, using compizconfig-settings-manager (available via apt-get), the solution (well, workaround...) is quite easy. It's possible to assign a screen side/corner to the "show desktop" function, the same way as the super-d key combinations is. So, it's quite easy to use the mouse to clear all windows and get to the desktop (and vice-versa). There's some extra Compiz plugins (also available via apt-get) to further tweak the effects, etc.

For more info, see: http://wiki.compiz.org/GeneralOptions