Neodymium magnets.  Be careful who you ship with when buying them from outside Canada.  If customs knows you are importing neodymium magnets they slap you with an extra fee.  When I ordered 40 dollars worth of magnets, the fee was 30$.  Turned a good deal to a shit deal.  Unpleasant surprise getting my package and having to go find some cash in my housecoat to pay the driver. UPS is bad.

How to save money on shipping with Canada Post

If you are sending a small package (one that will fit inside a mail box), you can print up the shipping label from home.  This allows you to grossly underestimate the size and weight of the package.  This can reduce shipping costs by half.  Saves a huge amount!