The Nikon deals get better and better every day. Amazon is currently offering 6% back in rewards when you purchase Nikon D4, D800/D800E body or the D600 kit which translate to $360 in rewards for the D4 ($167 for the D800). This savings comes on top of the already existing $200 off for the D800 body/D600 kit. Check this Amazon page for all details. This offer will be valid till April 13, 2013. The latest Nikon deals/rebates/savings can be found here.
Update: B&H now also offers 6% in rewards on selected Nikon cameras.