Potentiometer replacement

I would like to replace a potentiometer in a device with a digital externally controlled device. For example, replace a volume control on an amplifier with a digitally controlled circuit. I have tried an led-cds combo, but I would rather something that is directly connected. Any ideas??

Look for a "digital potentiometer" chip.

http://www.digikey.com/product-search/en/integrated-circuits-ics/data-acquisition-digital-potentiometers