So here's the math:
4,500 Gamestop/EB Games (some outside of North America)
3,256 Wal-Marts (USA stats only)
90 Rhino Video Games
786 Best Buys (US and Canada)
118 Future Shops (Canada)
32 Fry's Electronics (US)
635 Circuit Cities (US)
1447 Targets (US)
700 Toys 'r' Us (US stats only)
1 Nintendo World (New York City)
To come out with 11,565 possible Launch stores in North America. Of course, this doesn't include smaller chains and family owned businesses, but the results that will come from 1,000,000/11565 should give us a rough estimate on how many Wii's will be available at Launch in most stores.
It comes out at about 86 Wiis per store if we were to only include those chains. Of course, there will not be 86 wiis available at your local Wal-Mart in Hicksville, USA (or Canada), but it's nice to know that, if Wii distribution were communist, every major store would have 86 of them.