Even though it has been around for over 3 years, I just got around to trying out Skype, an internet phone service where you can make calls for free from one computer to another. I have to say, I was really impressed with the sound quality. As long as both sides of the conversation wear a headset with a microphone, it sounds just as good as a real phone call. Without a headset, it still works fine, but the other person sounds like they're in an amphitheater.
I tried it out with my mother and brother and we were able to have a 3-way conversation easily. My parents were amazed that the service is free and are now going to start spreading the news to all their friends and family. In fact, they immediately called my uncle who is going to be traveling to the Philippines, and told him to get it set up so he can talk to his wife back at home.
My brother has a webcam and Skype is able to offer video as well, but it doesn't appear to work in a conference situation. It has to be a one-on-one call. I think if you pay for a premium Skype service, you might get the ability to see multiple webcams in a conference call.
If you want to try out Skype with me, let me know...