I’ve you tried beryl or compiz you probably had notice that the Super key (the windows key, also known as Meta key) is used a lot. By default in my Fedora Core 6 installation the Windows key is not enabled, I had to add Option "XkbOptions" "altwin:super_win" to the InputDevice section of my /etc/X11/xorg.conf to activate it.
This is how the InputDevice section look like now:
...
Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
Option "XkbModel" "pc105"
Option "XkbLayout" "es"
Option "XkbOptions" "altwin:super_win"
EndSection
...