Although this project can only be described as possible overkill, Peter Lavelle has designed and documented a method of controlling relays using an Ethernet-connected Arduino and the web. The purpose was to switch between headphones and speakers on his PC, however this project is a natural explanation for another method of controlling Arduino-connected items over the Internet. As the control is via a web browser, it also opens up ideas with regards to home automation via web-enabled devices on a home intranet.
There is some circuit to build, however it is easily accomplished by a beginner. To move forward and explore for yourself, visit Peter's page here. And we're on twitter and Google+, so follow us for news and product updates as well.
Controlling almost anything is a reality with an Ethernet-enabled Arduino board, and at Freetronics we have what we think is the best one on the market - the Freetronics EtherTen. Apart from being fully Arduino Uno-compatible, it has onboard Ethernet, microSD socket, full USB connection (no pesky FTDI cables needed) and supports optional Power-over-Ethernet: