I am a Canadian living in the US with my American husband (LOL the opposite of your situation)!
Unfortunatly coupons in Canada are not flowing as much as they are in the US. I lived in Montreal and Sunday paper inserts were something I had never heard about before I moved down here.
I was a cashier for a grocery store when I was in college and most coupons came from the store flier or from inside the product/magazines. I also used the website that was posted above.
Happy hunting!