When working with the Arduno Uno, I often find myself needing more output ports than it’s got. Instead of having to trade my Uno for an Arduino Mega, I just plug in an EZ-Expander Shield, which plugs into three I/O ports and furnishes 16 — instantly providing 13 more I/Os. While each added pin can only safely consume about 6mA, this is still enough to drive LEDs or operate transistors. The documentation of this kit is extremely well done, with clear directions and photos. Assembly was a breeze. And with the provided libraries, you only have to add one line of code to your sketch to use your new expansion pins.