Digital SLR lens pricing?

I've been looking to buy a new wide angle zoom lens for my Canon dSLR & I've narrowed it down to a few lenses. Price is a big issue for me, but getting a good lens comes first. I recently bought a Sigma tele lens & was very impressed with the the build as well as image quality. Among the finalists so far is a Sigma 10-20mm that's within the price range I could handle. I know Tamron recently had a rebate program (now expired) where a comparable lens would have qualified, but I wasn't able to act then. Does anyone know of any mfrs. discount or rebate programs that typically are offered seasonally? I'd be willing to delay a purchase for a reasonable length of time if something might be available in the near future. Any thoughts or advice will be appreciated.