I recently crossed paths with a colleague I have known for a while who is now working at JAJAH, that has the tagline, “free.your.voice.”

If you goto the website, you will see that there is a really simple demo to show you how it works. There are plug-ins for Firefox that let you click on a phone number on a page to dial it, and a plug-in for the Mac AddressBook so that you can dial a number directly from there (Skype has a similar option, but you are using your computer with Skype rather then your phone)

They also have apps for your mobile phone so that any long distance calls from your phone route through JAJAH. Pretty cool!