The shield is designed for 'classic' Arduinos such as the Uno, Duemilanove, Diecimilla, etc. and uses the I2C pins on Analog 4 and Analog 5. It will also work perfectly with Arduino Mega R3's. Earlier Mega's have the I2C pins in a different location and will require you to solder two wires from the I2C pins on the shield and plug them into the different I2C locations.
This shield will not fit easily on top of an Arduino Ethernet because of the Ethernet jack height. You can use a set of stacking headers to give the shield more 'lift' above the jack.