Adorama takes $70 off a selection of Sigma 17-50mm f/2.8 EX DC OS HSM Auto Focus Wide Angle Zoom Lenses for Digital SLR Cameras. (Sale price is reflected on the product page.) With free shipping, that's among the best dollar-off discounts we've seen for these lenses. (We saw a similar Sigma lens sale from another merchant in July, but that was only $50 off.)

A best bet is the Sigma 17-50mm f/2.8 EX DC OS HSM Auto Focus Wide Angle Zoom Lens for Canon EOS Digital SLR Cameras (pictured), model no. 583101, for $599. With free shipping, that's $25 under our August mention and the lowest total price we could find by $70. Features include FLD glass elements, anti-shake, 11" focus, 1.5x magnification, and more.