Actually, I am doing it every week and this is really easy. Just pack everything good (since it long distance and package will be beaten) and go to post office. It will cost about 30 bucks for something under 1 pound and then ~ $5 for each additional pound. One "pain" - to fill customs declaration where you need to fill ~ 10 fields, like your name/address, their name/address, list content and how much it costs, date and signature.

That's it =)