www.UPS.com.
Their shipping software has all of the NAFTA
calculations/tariffs/taxes etc. built in. It's an invaluable tool! (Well they put a vaule to it.)
Don't forget
the IRS, they do have good resources. Mostly to keep you out of trouble.
If you use USPS their
manual is here.
also speck out Titles 15,16,39,49, and maybe 46 of the
CFR, Code of Federal Regulations. In order (Commerce and Foreign Trade, Commercial Practices, Postal Service, Transportation, and maybe Shipping) There are all sorts of tiny laws that will apply, but basically the CFR is a good reference, especially when you have to explain yourself. For instance the Domestic Mail Manual (DMM) is put forth in Title 39, and title 49 will tell you how you can ship batteries. -I know you already know what you need to know, but it pays to have some knowledge, especially when dealing with bureaucracy. Don't buy the CFRs. There is little that Canada requires. If you do any repackaging, you will need both English and French labeling. When in doubt, officials always refer to the more strict regulation, and that is usually with in the U.S.. I know little about American law and less about Canadian laws, but I am sure there is plenty of free help here. ->
NAFTA and other trade agreement help.
The only reason I have any knowledge is that I worked for a company that decided to ship internationally.
I'd still start with UPS.