Although I don't do it that often, I sometimes have to make calls to the US from home in the evenings.
This evening, for example, I've been dialed in to a call for about 3 and a half hours!
At present I'm using Skype, which works out pretty cheap and has the added advantage that I can use it on my laptop when I'm overseas.
Other friends are using services such as VOIPGate and JustVoip
Which service do you use and why?
Or is Skype the sanest (read - easiest) solution?