There are several new Sigma lens instant rebates that just launched up to $200 off. Check them all out here at B&H Photo.
The new Sigma 120-300mm f/2.8 DG OS HSM lens is available for pre-order in Canon, Nikon and Sigma mounts now for $3,599. Expected ship date is March 16, 2013. Hit the links below to B&H for more details.
It also appears to be in stock in the Sony mount option here at Adorama. Note that the Sony version does not include Optical Stabilization due to the built-in stabilization in Sony Alpha cameras; however, Sigma still prices the Sony mount version at the same price of the other OS versions.
B&H has the Sigma 30mm f/1.4 EX DC HSM lens for $289 (reg. $439) after a $100 price drop and a $50 instant rebate in all mount options. (Note the “DC” moniker means that this is for APS-C crop sensor cameras only.)
Hit up the links below for you particular camera mount.