Freetronics forum member Dave has created a great system to monitor the status of four mousetraps in the roof of his house. Instead of manually going up to check them, his mousetraps can now email him every six hours and say whether or not they have caught something. A microswitch is fitted to each mousetrap and held open with the trap. Once it springs close, the switch closes and therefore changes state. Every six hours an Etherten-controlled system polls the mousetrap switches and emails Dave what is happening. Ingenious!
As shown with the project above, Arduino and the Internet is made easy when you have the right tools. To get your Arduino sending emails a great start is the Freetronics EtherTen. Apart from being fully Arduino Uno-compatible, it has onboard Ethernet, microSD socket, full USB interface (so you don't need a costly FTDI cable just to upload a sketch!) and supports optional Power-over-Ethernet: