According to PokeBeach the pre-order bonus for Black and White may be Reshiram or Zekrom wall clings, at least at Toys ‘R Us. No other stores have confirmed any bonuses.
ALSO for those of you who will be watching the English version of the Pokemon anime the first two titles have been revealed: In the Shadow of Zekrom! & Enter Iris and Axew!
ps- In some minor 3DS news Nintendo has revealed that you may check your “Online Friends” list, take notes, and browse the web simply by pressing home while in-game! These activities WON’T make you exit out of the game. Nice huh? :3