The SN74HC165N is a neat little IC that will take an input of up to 8 parallel lines and produce a single, serial output. It's a great way to increase the number of inputs on a microcontroller. Project description, more information and ordering can be found at https://www.sparkfun.com/products/11512 Datasheet: http://www.sparkfun.com/datasheets/Components/General/sn74hc165.pdf Arduino Example: http://www.arduino.cc/playground/Code/ShiftRegSN74HC165N