I built a CheerLight!
So the idea is if you tweet to @cheerlights with a color, it'll change the color of my CheerLight (and everyone elses too!)
I used an Arduino and a ShiftBrite, with a sketch that responds to input via a serial connection, so it does rely on a computer running a Perl script right now. (I could switch it to use the Ethernet Shield if I get ambitious.)
The box is a plastic tray from a water painting set, with a black board on the front. I cut a piece of green construction paper for the tree, glued it onto the board to cover the hole I cut in it, and then glued a piece from a milk jug onto the inside to act as a diffuser. (I'll admit the enclosure was a total last-minute hack, and I'm working on designing a new one.)
There's a whole lot more info here: