Nintendo of America president Reggie Fils-Aime has confirmed that the Wii will use SD cards to store data - which is what the little door on the front of the console is designed for.
Speaking to US magazine Game Informer, when asked what the flap was for, Fils-Aime replied: "That is where an SD card goes. That's storable media. And on top are the attachments for the GameCube controllers."
But it won't just be SD cards you'll use to store data, according to Reggie: "It will be one of the memory mediums, and it's the only one that we've announced."
Could be the Wii remote will also store data, since Nintendo has previously suggested that each member of a household could have their own controller which remembers their preferred game settings. But until they make any proper announcements, we'll just have to wait and see...