This new app, Bobled, from T-Mobile let's users call for free from the iPhone or iPod Touch from anywhere in the world to a US, Canadian, or Puerto Rican number.
It's called Bobsled and the user interface is pretty simple and sweet.
Once you verify your email or log in through Facebook (something I hate doing, so don't even ask) you're free to use the app as you wish. It's supposed to have good quality sound. If you've used it before let me know what you think in the comments below.