B&H has a couple of good deals on some of the better Sigma lenses
In addition to the previously mentioned Sigma 30mm f/2.8 EX DN lens sale, B&H has the Sigma 19mm f/2.8 EX DN lens on sale for $149 (reg. $199) as one of its Cyber Monday deals. It is available for Sony NEX cameras and Micro Four Thirds cameras from Olympus and Panasonic. This deal ends Nov. 27. Check it out here at B&H Photo.
The Sigma 30mm f/2.8 EX DN lens for Sony NEX and Micro Four Thirds cameras is $50 off at B&H for Black Friday. The lens normally runs $199, but is $149 right now. I own this lens and highly recommend it for Sony NEX users. See my Sigma 30mm f/2.8 EX DN First Look Review.
Several Sigma lenses and speedlights are available with instant rebates up to $200. These deals are good through Jan. 15, 2013. Check out all the rebates here at B&H Photo.