Depending on the potential popularity of the game, other brick-and-mortar stores may offer preorders.
If, for whatever reason, the above two stores don't offer or stop selling preorders for a particular game, try Target, Walmart, Kmart or Toys 'R Us.
Preliminary numbers on the preorders of people who wanted to buy Wii Fit have proved successful so it stands to reason that the masses will buy Wii Fit.
GameStop/EB Games: It is unlikely that you'll find a great deal on a new game through this specialized store, but most locations will typically accept preorders for just about any game.
Amazon: Preorders don't have to be taken at brick-and-mortar locations!