74HC595 8-Bit Shift Register - Serial In Parallel Out

The 595 Shift register is a widely used 8-bit shift register. It is an easy way to lower the number of GPIO pins used from your Microcontroller. You get 8 outputs for the price of 3 pins, that's a savings! Plus you can daisy chain several of them and get even more outputs while using the same 3 pins. You can find a great tutorial for the arduino and the 595 over at arduino.cc.