If you're hooked on using Jajah, a VOIP service that gives you lower long-distance rates, you can now get easy access to it directly from your iPhone. When you point your Safari browser to iphone.jajah.com, you can type in the number you want to call or select the name in your Jajah contacts. Jajah will then call your phone, you pick up, and then you will be connected to the desired international number.
What's great is the fact that you can call any phone anywhere in the world without needing an international calling plan. Registration is free and there is no software to install or contract to worry about!