If you're sending *into* Canada, harass Canada Post. 1-888-550-6333 during EST business hours. Right now I've got one that I sold AWOL at the border containing a hard drive, but USPS claimed to know nothing about it, so Customs somewhere is making me look like an ass. :|
Use USPS or Fedex to ship to Canada. You'll pay taxes - that's invitable and lying on the form is grounds for federal fraud charges - but at least you won't be hit with an extra duty fee unlike UPS.
- M4H