Switch monitor resolutions with a single mouse-click

If you have an external monitor or projector that you occasionally attach
to a notebook computer, you might be used to switching resolutions
on a regular basis. Unlike with Windows, this isn’t just a right-click
procedure—you must navigate the System → Preferences menu.
A good solution is to use Synaptic to search for and install resapplet. For
some reason, although it’s officially a GNOME applet, resapplet doesn’t
appear on the standard applet list. Instead, it must be configured to
start at login. To do this, click System → Preferences → Sessions,
ensure the Startup Programs tab is selected, and click the Add button.
In the Name and Command fields of the dialog that appears, type resap-
plet. Leave the Comment field blank. Then close the dialog box and log
out and back in again.
The new icon will then appear besides NetworkMonitor in the notifica-
tion area. Clicking it will reveal a list of possible resolutions that you
can choose-from.
Incidentally, it should be possible to instantly step up and down reso-
lutions by typing Ctrl + Alt and tapping the + / - keys on the numeric
keypad. Unfortunately this doesn’t work on Ubuntu systems because of
the way they graphical subsystem is configured. It may work on other
Linux systems, however.

Taken From Ubuntu Kungfu