74HC595 Shift Register

74HC595 DIP-16 8-bit SIPO (useful for controlling a large number of outputs) Shift Register allows you to control led segments, led matrixes and other devices with a lot of pins using less wires and less pins of your Arduino.  For inputs (buttons etc. you will need a PISO Shift Register such as the 74HC165).

Instructables has a nice tutorial for Arduino and Shift Registers. (Updated to tutorial with this particular shift register).

Bildr tuorial controls 8 leds (instead of 16 in Instructables example) but it is easier to wire and chain to new 74hc595’s…

Sparkfun page on shift registers.

Datasheet

Shift registers