Show all open windows in 11.04?
Super+W can do it but if you want to add Mouse Gestures to it, Like Gnome 3 you can do the following:
(as pointed out in comments)
Install Compiz Settings Manager
Run it, Go to Commands under General
Set Command 0 in Edge Bindings and come back to "Command" tab
Enter "xdotool key Super_L+w" in Command Line 0
Install package xdotool
Install compizconfig-settings-manager.
Then
scale plugin > bindings - initiate window picker or initiate window picker for all windows, choose the edge binding
use the window symbol + W this will show all open windows