Shipping charges range between $4.99 US and $7.99 US per shipment, plus an additional $1.99 US to $3.99 US per item. An import fees or duties that may apply will be visible during the checkout. The full Canadian shipping details can be found here. Amazon.com's prices are quite competitive to begin with, so even with the shipping and import costs, deals are bound to turn up for Canadians. The strong Canadian certainly helps, too.
You can see the entire Canada-shippable product selection from the first link, but you can also identify whether or not a given item ships internationally by looking in the "Product details" section. Under shipping it will say "This item is also available for shipping to select countries outside the U.S" or "Currently, item can be shipped only within the U.S".
A big thanks goes to Al Kaseltzer for spotting and sharing this!