I got one of these 'Softpot' membrane potentiometers recently as a way of telling where a finger is pressing on a strip. I rigged it up like a normal pot and it worked but was pretty noisy, I put a capacitor over a couple of the pins and it seemed to help a lot. Then I read that if you press at the top and bottom you can create a short circuit and it gets hot, so I had to try it... It did indeed get exceptionally hot very quickly and as I don't particularly want people to burn themselves or fry the strip (it's not cheap!) I tried adding some resistors. The more resistance you add the more resolution you lose so I settled on the circuit below which seemed to do what I want it to. Besides that, you can read it in Arduino like a normal pot (check the AnalogInput example), though there is a bit of 'floating' when you have taken your finger off that you have to deal with.