I like this new site a lot because it includes shipping and taxes in their price comparision.
http://www.photoprice.ca/
The price differences for camera equipment between Canada and the U.S. are so large that it often pays to shop outside Canada even after shipping and taxes.
For example, the price difference for a Sigma 70-200mm f2.8 is about $400 or 40%, after shipping and taxes, according to this comparison website.