With Canada Post’s high rates for parcel shipping, you may be tempted to cross to the US and ship USPS if you live near the border.  If you do this, be aware that bringing goods across the border that have been sold is considered a commercial entry and you are subject to a $10.75 user fee.  If carrying commercial goods, your car is considered a commercial vehicle and you can NOT use the Nexus lane.

https://help.cbp.gov/app/answers/detail/a_id/1281

http://www.cbsa-asfc.gc.ca/publications/pub/bsf5095-eng.html#a04_1

If you have personal items you would like to ship with USPS, Priority Post service offers 2-day, tracked delivery and free boxes.  First class mail also has free tracking.  Though prepaid online postage is cheaper, it is not available to Canadians.  USPS does not allow non-US payments and Paypal’s USPS label no longer works.  Postal calculators can be found on the USPS website.

If you are in the Greater Toronto Area, Chitchat’s Express offers US shipping service.  Books To The Border may offer a similar service in Greater Vancouver but their website is seriously lacking information.