I got a copy of the 'A Customer's Guide to Mailing' from my post office & USPS sent me a copy in the mail. It has alot of good/useful info in it...
In this guide, it says that packages that weigh one pound or more must be handed to your letter carrier or taken to a Post Office.
You can print out Media Mail/Parcel Post E-Labels & pay 13cents... You have to d/l the shipping assistant..It's pretty neat. It has a place to figured shipping cost,,,you put in your zip code, zip of destination, sevice type & weight. It will tell you the zone & how much it will cost...Also calculates International rates, how many days it will take for the buyer to receive their package. Here is the addy to d/l it.
http://www.uspswebtools.com/Shipping.../SA_splash.htm