This is the Tetris Stackable LED Desk Lamp available from ThinkGeek ($40). You can stack the pieces however you want, and they light up when they make contact with the pieces below. And in case you were worried, yes, it is an OFFICIALLY LICENSED Tetris product. Personally, I would have called it the stackable block desk lamp and kept the licensing rights money to myself, but that's just me and I'm a shrewd businessman. "You just traded a $5 bill for four singles." MORE MEANS RICHER.
Keep going for a couple more shots and a video.
Thanks to King of All Geeks, who I suspect is self-proclaimed, but possibly competed in some sort of geek trivia competition.