B&H has deals on a few Sigma lenses going on now through June 17.
Sigma 50mm f/1.4 EX DG HSM $399 (reg. $499)
Sigma 10-20mm f/4-5.6 EX DC HSM $429 (reg. $479)
Sigma 70-300mm f/4-5.6 DG OS $259 (reg. $359)
Additional deals include the 30mm f/1.4 EX DC HSM for Sony and Nikon mounts for $289 (reg. $489). This one expires May 31. This is a clearance item and may not be around much longer anyway (the Canon version is already listed as discontinued). Check out the Sony mount here and the Nikon mount here.