The arduino port expander shield is an I2C shield that adds 16 digital outputs to your arduino. You could use it to control LED's although it was initially designed to control SSR's on an aquarium.

Videos:

Overview

Demo:

Features:

• 16 digital outs
• Address pins are pinned out
• Up to 3 shields (6 total) may be used for a total of 48 digital outputs

I2C Port Expander Shield Kits are available here

I2C Port Expander Shield Assebled are available here

Schematics / PCB:

Download