I went down to the post office today and did a wiretransfer for 780 yen. The only bad thing is you have to fill out this long ass form.. I do it every month, and I usually get 2-3 extra forms as I run out... fill them out in advance and as soon as I walk in it takes about 10 minutes. But if I forget a form you can tack on another 5-10 minutes to fill it out.
You only need to present and ID card, and the yen to send it. I think that is the cheapest way to send money from all the services I have seen. It's wired into a bank account ( you gotta know all kinds of info, account numbers, addresses, branch names etc...)
I forget the specific name of the forum, but I can get it if you are interested.