VoIP provider Jajah has released a web app today that helps you make international calls on an iPhone without going totally broke. The Jajah web app looks like the iPhone's dial pad, and like the iPhone it uses an address book to store contacts. After selecting the person you want to call, though, things get a little funky.
You hit the person you want, then Jajah calls you back and acts as the middleman, using VoIP to connect you to the other party's landline. You are still using your plan's minutes on top of Jajah's VoIP rates, so it makes no sense to use this for calls within the US. While calling cards provide less expensive options to communicate with people overseas, you don't always have a card. This is more of an option of convenience, letting you worry about things other than calling card PIN numbers.
Another advantage is that Jajah members may also call other Jajah members for free, that is, without paying the VoIP service fee. While Jajah's product is far from perfect, it's a start. Personally, I won't even consider using it until they lower the price of calling Djibouti from $13.77/minute. [Jajah]