A friend emailed me a few weeks ago about a service that allows you to make a call to an Iowa number here in the States and then dial out from there to international numbers for free. It's called Futurephone.
I was wondering about its legitimacy, and I found an article by David Pogue, technology writer for the New York Times, on it. See the comments on his blog here.
The Futurephone website has a list of countries that you can call using the service, and Japan and Taiwan are on there, but it hasn't worked for me. I get an error message every time.