NVIDIA configuration utility
I really don't understand why this program it is not installed by default when you install/ enable the NVIDIA proprietary drivers on Ubuntu.
I was going mad trying to configure the resolution on Tango, hooked up to my external monitor, nothing worked, and was only able to clone the output from the laptop's main screen, even the resolution, which looked like sh*t on the big one.
It looks like, in order to use different resolutions (and to be able to not use the screens on clone mode) you have to install the NVIDIA configuration utility.
To do so, type:
sudo aptitude install nvidia-settings
Once opened, the configuration utility looks like this (at least, its main window):