Expose (OSX Style) Functionality in Unity
Solution 1:
Super+W should automatically be set in 11.04 (Super is the Windows key on most keyboards). If that doesn't work, look into the CompizConfig Settings Manager (install) and search for "Scale" to change various settings.
Solution 2:
Scale plugin. All settings are here -
CCSM > Window Management > Scale
sudo apt-get install compizconfig-settings-manager
if you don't have it already