A system just isn't a system until it has a version of Tetris (and no, hacks don't count), so it's a good thing Nintendo that Hudson has announced a multi-player Wii Ware version of the game (PDF link).
A translation of the announcement by our good friends over at Engadget Japan reveals support for up to six Wi-Fi players, planned downloadable content and gameplay-altering items activated with Wii remote shaking. Hudson says they expect at least one million downloads for the title after it's simultaneous worldwide release this summer (for an undetermined price). If you just can't wait and/or pay, may we suggest the free and/or currently-available Tetrinet.
Read - Japanese PDF announcement