Find a US billing address

I'm in Canada, and have wanted to use features such as Amazon.com's
"Marketplace" (where you can click on any book title and pick "I have
one to sell"). Many require a U.S. billing address, however (a U.S.
bank account is no problem as many Canadian bank U.S. dollar chequing
accounts are encoded for U.S. processing and clearance). Part of
Amazon.com's reply to me when I asked about this was:

***
We do have International sellers who have established U.S. checking
accounts and U.S. billing addresses, enabling them to receive payment
via Amazon.com Payments, and who are currently enjoying the
benefits of this service.
***

My question is: How are Canadians (or anybody else International) able
to set up a U.S. billing address beyond, say, having any friends or
relatives down there? Is there some sort of intermediary or Brokerage
service that allows you to establish a U.S. billing address in your
name, and either forward the mail to you (if any physical mail is
actually ever sent - many times it's not) or just receive it?

Any suggestions or ideas appreciated.