I though about using the Raspberry Pi to switch on and off other electrical devices which unnecessary consume power in stand-by mode. In short, I'd like to control an AC socket or multiple sockets. How can one let the computer "push the button":
Image: CC-BY-SA 3.0 by Firstfreddy
The physical solution is a relay, but I don't want to build all on my own and play around with 220V and sparks when switching on and off ;-) By the way the Raspberry Pi requires 2 Watt in idle mode, so only using it as a switch to save energy might not make sense, so it should be usable for other purpose at the same time.