U.S. pre-orders start TOMORROW (10/13) for $50 deposit, Canadian pre-orders begin on Monday (10/16) for $200 CDN cash/credit or $50 CDN trade-in.
Gamestop/EB Games has just announced that they will begin accepting Wii pre-orders at their U.S. retail stores starting Friday, October 13th. These pre-orders will be registered on a first-come, first-serve basis, and a $50 deposit is required (this deposit amount can come from cash, credit, or trade).
You can also trade in 3 Xbox/PS2/GameCube/DS/PSP games and get $10 extra credit towards reservation of a Wii, or get 20% more trade-in value for games traded in towards a purchase of a Wii console or the Wii version of Legend of Zelda: Twilight Princess.
EB Games Canada will begin taking Wii pre-orders on Monday, October 16th. For a reservation you either have to pay $200 CDN in cash/credit, or trade in $50 CDN worth of games.
For both countries there is a limit of 1 reservation per household.
Note that this round of pre-orders are for Gamestop/EBGames' retail stores ONLY - online pre-ordering will take place "at a later date". They strictly state that a reservation does not guarantee receipt of a system, saving themselves from customer heat like they had last year when they wound up taking more Xbox 360 pre-orders than they could fill.