USA lower 48 states & Canada, USPS PARCEL POST is both inexpensive and reliable, reaching most of the lower 48 in 4-5 days, a little longer for Canada. For rush orders select USPS PRIORITY MAIL.
Other countries, including Europe, UPS would be the best choice, but can be rather expensive.
To save a bit use USPS Expedited Priority Int'l, which has full tracking.
If you have any questions please feel free to email at firstname.lastname@example.org