We love using Skype both at our office and at home. You download it for free and if the person you're calling has it installed in their computer you can call each other and talk for free...and the sound quality is excellent!
If the person you're calling doesn't have a computer or is away from it you can buy "Skype Out" credits and use Skype to call that person on their land line or mobile phone from your computer. Calls within the continental United States will cost $0.022 per minute. And that's also what it'll cost you to call from the USA to the United Kingdom. You buy Skype Out credits in Euros but they translate to above dollar amounts.
With Skype we've been able to keep in touch with soldiers overseas, students away at college, publishers we deal with, and the calls we've made have been very inexpensive. A 27 minute phone call we made to Azerbaijan, at a rate of €0.17/minute, was €4.64 or a little over $5. An 8 minute call to a mobile/cell phone in Germany, at a rate of €0.25/minute, was €2.26.
We've had excellent service from Skype since we installed it on our office and home computers in 2004. You can click any of the links on this page to go to their site and sign up. We hope your experience with them will be as good as ours has and continues to be. It's a CCF Top Pick!