B&H Audio Video offers the Sigma 50mm f/1.4 EX DG HSM Lens for Canon, model no. 310101, for $349 with free shipping. (Amazon offers it for the same price.) That's tied with our July mention as the lowest total price we've ever seen. (It's a curent low of $50.) It features a hyper sonic motor for silent, high-speed auto-focus.

Update: The price has increased at B&H Audio Video; however, Amazon still offers it for $349 with free shipping.