[Czar]

Jajah offers a similar service, but there are only apps for specific phones (e.g., Motorola, Samsung, SonyEricsson, etc.). Their rates seem cheaper overall, though. For example, Aruba mobile to US is US $0.187/minute. There are also a bunch of cool apps for Google, Mac, Firefox, etc. You can make calls via their website (there's a WAP version). You get about US $0.66 free credit when you register. The first call I made to check my VM at work went well.