Quickly place a window to another screen using only the keyboard

1. Install CompizConfig Settings Manager

   sudo apt-get install compizconfig-settings-manager
   

2. Run CCSM → Go to bottom (Window Management) → Go to "Put."

3. Enable the plugin.
4. Configure shortcut for "Put to next Output."
5. Log out and back in again.

If the plugin put doesn't appear in CCSM, install the compiz-plugins package. (sudo apt-get update && sudo apt-get install compiz-plugins)

EDIT: The required plugin package is now called compiz-plugins on 12.10 and higher. compiz-plugins-extra is still used for 12.04.

I like Put to next Output with Ctrl + Alt + n

enjoy it!

Put at CCSM.

Put to Next Output

On my machine (CentOS Linux 7) it worked out of the box:
Use window key+shift+arrows this will move window quickly between monitors Works on maximized as well as non maximized windows.