Ubuntu 9.04 comes with some visual effects from Compiz turned on by default. This post contains a list of the key combo’s used to active some of them. Compiz also offers many other “cool” effects. If you install the compizconfig settings manager you can enable/disable all of the neat effects (most of which are eye-candy, and not really useful).
Note: The “Super” key is typically labeled with a “Windows” logo on most keyboards.
Expo: Super-E will show all of your desktops at once, and you can drag windows from one to the other. Arrow keys allow you to select a particular desktop, and the enter key will zoom back to it.
By default, as you move windows they will “snap” so that their edges are aligned. To disable this behaviour, hold the SHIFT key down when moving windows.
Allows you to switch between desktops using the CTRL-ALT-
Enhanced Desktop Zoom: Super-button 2 (typically, button2 is the middle button) will zoom in a LOT! Super + the scrollwheel (if you have one) will allow you to zoom in/out a bit less. If you would like to use the keyboard for zooming, you will need to install the CompizConfig Settings Manager and enable keyboard zooming.
Negate: Negate (black is white, white is black) a window or the whole screen. Super-n (window) or Super-m (screen). Useful for increasing the contrast of text, or just making people wonder what is wrong with their desktop.