Copied from elsewhere:

Make free international phone calls sans Skype with Futurephone, a company that's just got to be bleeding money.

The service doesn't run ads or ask for personal information. They simply provide an access number based in Iowa - so domestic long distance charges apply - that you call with any old phone and then dial your international number through.

Call 712-858-8883 to give it a try.

I haven't been able to test it myself, but the New York Times' tech writer David Pogue says it's totally legit. Cool! You got a friend overseas? Give Futurephone a try and let us know how it goes. (Warning, though: calling international cell phones doesn't yet work.)

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Assume it to be operated by the NSA as a honeypot to trap terrs calling Osama, and speak accordingly. In the meantime, have fun gabbing for free. :)

Ah yes, I happen to find Daily DIY quite the useful blog myself. It should be noted that the phone number listed above is located in Iowa, and hence, anyone who can make affordable calls there can use this suspicious, but none the less useful service. That also includes Canadian callers, particularly those with "borderless" phone plans which allow them to call US & Canada at their local rates.

Lucky you, that you can call for free or cheaply ;)

Reminds me of a little dream I had:

Our school 's central had a bug which allowed us to dial at school, pressed "0" ( which was used to dial out ) waited for a dial tone and then dialed a phone number of some cell phone.

Some companies, including hospital were known to had the same bug, but they fixed it all.

We were able to call to cell phones at the price of local calls or even to foreign country's.
Unfortunately, they got suspicious because of big phone bills every month, so they fixed it.

But we had a lot of fun while it lasted ;). We sometimes called some schoolmates and told that we are calling from school. When they would look up for the number in the phone book, they saw, it was really from school. :D

It was very convenient for hiding your own number, behind school's one when making prank calls :D ( what can I say, we were still a bit childish, but we laughed out pants of :p )

Is this service you mentioned a similar bug?
If you are using it, be careful not to reveal anything about yourself, they could be listening ;)

And you have to remember:
Nothing in this life is for free, or almost nothing.
They probably have some benefits from the service.