I subscribe to an excellent magazine from O’Reilly called MAKE Magazine. It is aimed at DIY hobbiests, and includes things such as how to build your own portable Atari system, and how to build a digital camera for kite flying.
It also includes articles that can cause more harm if you don’t know the basics of electricity. And even if you follow the instructions, you could still get in trouble if you think that is all you need to do, as referenced by the following email I got yesterday:
The “How to Build a Power Tap” page in MAKE 05, page 112, contains an error that could cause an unsafe wiring situation. Before attempting this project, please read the corrections posted at http://makezine.com/05/quickanddirty.
PLEASE DO NOT BUILD THE POWER TAP AS SHOWN IN THE ILLUSTRATION.
The illustration shows a dual plug receptacle, which, when wired improperly, can cause a short circuit. Do not attach the wires from the extension cord to the screws on the same side of the receptacle, because it will create a short circuit.