If you're looking to control all manner of devices using relays and wish to do so remotely over the Internet - consider the new tutorial by John Boxall over at tronixstuff. He has used out new RELAY8: relay control shield in conjunction with an Ethernet-enabled EtherTen board to create a system that can be controlled via http using the teleduino service. First the article describes how to control the shield locally using I2C, and then sending those commands remotely. It really is quite simple, and the teleduino service is free to use.
So what is the RELAY8:? It's a new Arduino shield that allows you to drive up to 8 relays from your Arduino using just 2 I/O pins with this shield. It communicates with your board using I2C, so you can even stack several shields together to drive 16, 24, or more outputs! Includes back-EMF protection and works with a wide range of relays. Perfect for home automation projects! For more information and to order, click here.