From: http://bildr.org/2012/11/touch-sliders- ... t-arduino/
You all know the potentiometer, you turn it, and you can read on your arduino where it was turned to. Well 3M makes a product called the softpot that is a linear touch potentiometer. So instead of turning a knob, you touch it.
The really nice thing about these is that they are great for prototypes because you can tell where someone touched it. So if you place a piece of paper with some printed buttons over it, you can mock up surface touch ...