Here is a very useful tool of the Post Office (worth bookmarking it) --
Postage Rate Calculator --Domestic and International Postage Rates
http://postcalc.usps.gov/
It is very handy. You start off by selecting the country in the drop down menu. The rest is self-guiding.

By the way, I made this Guide for eBay -- "Introduction to Printing PayPal Shipping/Postage Labels." It contains a lot of information and suggestions about the Post Office's classes of First Class mail, insurance, Delivery Confirmation, etc. You get to it by clicking this link:
http://reviews.ebay.com/Introduction-to-printing-shipping-labels-and-postage_W0QQugidZ10000000004429200
If you find it helpful, vote "YES" at the bottom of that page. Thanks.

Robert