A very easy logic level converter to translate I2C signals from, say, a 5 V Arduino to a 3.3 V slave device.
24.8.13
I2C LED Display From Hacked Voltmeter
LED voltmeters are a cheap source of 7 segment displays and can easily be repurposed. Using the I2C protocol, a master microcontroller such as an Arduino Uno can govern multiple displays with just 2 I/O pins.
