I have been jealously watching my American friends downloading the Amazon free app of the day (which is actually a pay for app made free for a day) from Amazon.
I am happy to report that the Amazon Android App Store is now open to us Canadians. You will have to a setting on your device to "Allow Unknown Sources" to download the Amazon app store app.
You use your standard Amazon.ca account to sign in.
Download the Amazon App Store App here.
I tested the purchase process by "buying" todays free game 10000000 (which failed in the past saying the store wasn't available to me) and it worked.