is one thing, but the recently-revealed Twilight Princess exploit allows all sorts of unsigned code to run natively on the Wii. Homebrew developers are already starting to take advantage, releasing a bunch of interesting and/or useful unauthorized programs for Nintendo's little white box. Among them:
Wii Tetris - So much cooler than Pong. No, you shut up!
Still no public announcement from Nintendo in reaction to the exploit, though given their recent aggressive pursuit of game pirates, you can expect a PSP-style battle of the firmwares to start any day now.
[Thanks to reader Craig for many of these links]