I bought myself an Arudiuo, it cost about $30 and basically lets me prototype electronics. It gives me a whole heap of input and outputs that I can use to input stuff into the computer, output stuff from the computer or just have it running by itself.
The first project I built was just some LED’s and flashing them, this second project is an 8×8 LED Matrix that I bought online off ebay. It cost me $16AUD with free postage for 10 of them.
Here is a video of it in action: http://www.youtube.com/watch?v=dYZcLuxIiZ8