I'm having to do a lot of this at the moment in the U.S. from the U.K.and find that the cheapest way to do it is via paypal - both you and the recipient have to be members. In my case, I have a friend in the U.S. who sends $ where I ask him and then I reimburse him by a request to my paypal account. It is very cheap and although some do not like the system (which is really a way of paying for goods on e-bay), I have never had problems.
P.P.