Long in the tooth, not really relevant anymore, and ultimately - like so many good things - strangled by Microsoft's acquisition and long neglect, but RIP to a great.
If the idea of paying several dollars a minute to call somebody in the next town or across the country or on the far side of an ocean is completely ridiculous to you, this software is why.
Skype was a goddamn miracle when it came out, an absolutely world-changing piece of software.