BestBuy now lists the Nikon D800 as available for order, but not available for shipping (it was listed as "sold out online" yesterday). You can check the "Shipping & Availability" link for the stores in your area where you can pick up the camera after purchasing it online. All stores in my area did not have any in stock, but you may get lucky. I believe the second shipment of D800 cameras is now hitting US stores - several non-NPS readers have already reported receiving their camera in the past few days. BestBuy doesn't keep a pre-order list, so there is a good chance that you may find one.
The Nikon D4 is still listed as "sold out online" but some readers were able to purchase it from BestBuy's website few days ago.