San Jose maker Robert Quattlebaum bought a string of LED Christmas lights from Costco, and not liking the preset lighting programs that came with the set, he hacked the lights and wrote his own programs.
This string contains fifty “bulbs”. Each bulb contains a red, green, and blue LED–allowing for any color to be produced. The biggest drawback is how you control them: there are 14 pre-set “programs” that you can select, and they are all pretty lame. However, with a little reverse engineering and an Arduino (or any other microcontroller) they can be made into the coolest Christmas lights on the block. If you buy several strings, you could easily make a large 2D LED array. The possibilities are endless.