(From the NRA-ILA's page:
http://www.nraila.org/GunLaws/FederalGunLaws.aspx?ID=60 )
Sales Between Individuals
An individual who does not possess a federal firearms license may not sell a firearm to a resident of another state without first transferring the firearm to a dealer in the purchaser's state. Firearms received by bequest or intestate succession are exempt from those sections of the law which forbid the transfer, sale, delivery or transportation of firearms into a state other than the transferor's state of residence.
My understanding is that you can send it via common carrier (NOT THE POSTAL SERVICE) directly to a FFL in your buyer's area. It shouldn't cost YOU (the seller) anything. All of the paperwork/phone calls are done at the buyer's end, and at his expense.
You can call the NRA-ILA at 800-392-8683 just to make sure.