Jack Christensen sent me one of his One Million Ohm's kits, so last weekend, my son and I decided to put it together. Well he made it and I got in the way and 'hovered' like a typical dad.
Just kidding. The big resistor in the middle, serves no more purpose than being the butt of the joke. It is surrounded by four LEDs that flash in various patterns controlled by two buttons. The whole thing runs from an ATTiny and includes pads for attaching ICSP headers if you feel like hacking it.
WARNING: When constructing this project, always remember that Ohm's Law dictates that V = IR, so if you can persuade just 100mA to flow through it, there will be 100,000 Volts generated!
Its really easy to put together, and a great first soldering project.
It includes everything you need, except a pair of AA batteries, and my son very much enjoyed putting it together. The only things to watch out for are putting the LEDs and chip the right way around.
Some of my books, that may interest you: