The Nintendo GameCube Mic will be bundled with Mario Party 6 when it ships on December 6 for the Gamecube.
From GameSpot, "The entire cast of playable characters from Mario Party 5 will return, including newcomers Koopa Kid and Toad. A new day-and-night system will change the nature of the boards and even the gameplay of the minigames. And the gameplay has been speeded up, with less "downtime" between the board game and minigame sections."
"As for the use of the microphone controller, all that has been revealed is that there will be a separate 'mic mode' where players use the microphone to answer quiz questions. Whether or not the mic will come into play during the multiplayer party mode or single-player story mode is not yet known."