If you're outside of Canada, here's a site offering favourite Canadian groceries shipped wherever you happen to be! Although I didn't think that Cheerios and Kraft Dinner were uniquely Canadian.
If you're looking for the Smarties, you'll have to look under Chocolate Bars, for some reason, not candy.
I liked this page of Vachon Snack Cakes--Canada's answer to Little Debbies. They were pretty common lunchbox currency when I was growing up: Flakies, Jos. Louis, and Lune Moons. Actually they're called 1/2 Moons, but because of bilingual packaging (you can see it in the photo there), we always thought they were called Lune Moons.
And of course Viva Puffs and Wagon Wheels--more childhood stuff that we (very occasionally) buy, supposedly for the kids. (Dare Ultimate Fudge Cookies are one of Mr. Fixit's deepest, darkest secret cravings. But don't tell him I told you.)