All About U.S. Import/Export

The Customs and Border Patrol people have a lot of info online. Under the Imports section, they list the duty required for items entering the U.S. (Harmonized Tariff Schedule).

And regarding paying duty on gifts:

It comes as a rude surprise to many people that recipients of gifts mailed from abroad will have to pay any duty owed on the item before they can receive it. Duty cannot be pre-paid by the sender (duty can't be paid until the duty rate is assessed by a Customs and Border Protection (CBP) officer. This can't happen until the item actually arrives in the U.S.), it can only be paid by the recipient. We are aware that this can place the sender in an awkward position, but there is nothing CBP can do. We suggest you include a note with the package offering to reimburse the recipient for any CBP duty they are charged. For more information, please see our brochure, "International Mail Imports" under the Publications section on our web site at www.cbp.gov.

This can bite you in the butt if you send a $200 item but mark it up to $700 on the customs form for insurance purposes (particularly for something that has primarily sentimental value). The recipient will have to pay duty. This happened to me, and it sucked...I knew the item wasn't valued at $700, but I had to pay something like $50 in duty, high in part because it was a textile item.