Pressing and holding Alt + scrolling with the mouse wheel used to give me a transparent window, is there any way I can get that or something similar in Ubuntu 12.04?
Install these pacakges with this commands
This will install the CompizConfig-Settings-Manager, you can find this by searching as CCSM in the dash.
Open the CompizConfig-Settings-Manager by typing ccsm in the dash. In the CCSM's window, under the Accessibility section, enable the Opacity, Brightness and Satuaration by placing a tick mark on the corresponding checkbox.
This should automatically enable the plugin, if it is not, press Alt+F2 and type
Now you can increase or decrease the transparency of any window by holding the Alt key and scrolling mouse wheel.