DIY Arduino oscilloscope using Nokia 3310 LCD screen posted a cool hack that can be done in an afternoon if you have the parts handy.  The author built a DIY oscilloscope using an Arduino Pro Mini and the LCD from a Nokia 3310.  The Arduino is wired up to sample from an ADC port and writes those values to the screen to create a waveform.  Two potentiometers control the sampling speed and input voltage for approximate time and amplitude scaling just like the real thing.