Myles recently ported an open Tetris clone to the Arduino. We added support for the Nunchuck (so now it works with both the Nunchuck and the Classic Controller) as well as music!
Arduino Tetris on the Video Game Shield – [Link]
PICtris project is a tetris game using dot led displays controlled by a PIC microcontroller. PIC18LF4520 is drawing 2D graphics on LED display and four buttons control and rotate the blocks. Find schematics and source code on the link below.
PICtris: Tetris on a PIC MCU - [Link]