Each country has it’s own quirks, and their address format is no exception. As much as I would love to impress everyone with my vast knowledge of the ins and outs of international shipping, I’ll just post my knowledge base. And the curtain flies back to reveal that the Wizard was sadly, just a man…

UPU arsgwe This site has an easy to use and understand address format search for any country that is part of the UPU (which is most). They also have downloadable guides and you can print off information for individual countries (so 1 page as opposed to 100). Click here to visit the Universal Postal Union website.
UCSanDiego arsgwe UC SanDiego has an amazing Mail Services website, and one of the best pages includes a step-by-step on “How to Send USPS International Mail“, including all the available services of mail. I was half tempted to duplicate the steps for this page, but I figured that I should give credit where it is due considering that they did all of that work 😉
FedEx Purpl arsgwe Although I try my best to be impartial when it comes to promoting one vendor over the other, I have to say that I will choose FedEx International over the other vendors most of the time because of there very elegant shipping system. This link will take you to their International Snapshots page where you can select the country you are shipping to and learn about regulations, restrictions and prohibitions for shipping to that country.
usps-logo arsgwe The Post Office has worked tirelessly to update their website as user friendly as possible, which is quite the feat considering the volume of information they must communicate. The link provided here will take you to “Preparing International Shipments“. This provides a step by step process on how to send USPS International Mail, provides links to fill out customs documentation online (highly recommended), order shipping supplies and details about Military and Diplomatic mail as well. 
arsgwe I stumbled on this site in my never ending quest for accurate China postal codes and have found it to be one of the most consistently useful (and accurate) foreign address website. It’s only for China addresses, but it’s simple and easy to use. I highly recommend using this site for all shipments that you send to China. Or just to learn more about foreign addressing. ‘Cuz who doesn’t love studying that?: China Post