GameStop has begun taking pre-orders for the Nintendo 3DS. The system itself still does not have a concrete release date but sources state that should be sometime in the Spring (March-ish). The system does not have a definitive price at this point either.
But if you are less concerned with small things like price and release date, GameStop will be happy to take your pre-order for one of the handhelds. You have to do it in person, the GameStop website is not taking pre-orders as of this time.
Currently, the retailer is accepting down payments in the varieties of $50 and $25 depending on where you are geographically situated.