Adorama has the Sigma 18-250mm f/3.5-6.3 DC Macro OS lens for $260 (compare to $350) through May 27 using the coupon code at 260SIGMALS checkout. You must use this couple code in order to get the deal price.
B&H has the Sigma 18-35mm f/1.8 lens back in stock for Nikon DX mount cameras. Check it out here at B&H Photo.
B&H has the Sigma 70-300mm DG OS lens in Nikon mount for $199 (compare at $359). Check it out here at B&H Photo.