Adorama is taking orders NOW via THIS LINK.
B&H is now taking pre-orders too
The Nikon D4 has been announced and B&H has created a great page that offers info about it here. You can pre-order now which usually means B&H is expecting to get a decent size shipment in. I suspect this means earlier rumors about it shipping at the end of February are true so if plan to plunk down $6k for one then you’ll want to get in line as soon as you can as I’m sure the pre-orders will be nuts.
I’ve seen no official word on the D800 yet. Here’s what’s on Nikon’s site about the D4 though.