I hadn't touched a soldering iron in years, but reading Make Magazine inspired me to pick one up and start playing again. I read an article about this persistence-of-vision kit. It uses an Atmel ATtiny2313 Microcontroller to cycle a bank of 8 LEDs through a pattern at about 400Hz. When you waggle the board from left to right, the persistence of your vision causes you to be able to read the message encoded therein. The kit is from Lady Ada, and I highly recommend it if you're new (or really rusty like me) at the old electronics game. It was cheap, fun and quick to build, and it didn't need any expensive tools. It is also reprogrammable, so you can tweak the C code, with free tools, and update the firmware from the parallel port of your computer. Not only that, but once you're bored of the POV thing, you can reprogram the microcontroller to do something else.