Skype is the next phenomenon from the people who brought you KaZaA. Just like KaZaA, Skype uses P2P (peer-to-peer) technology to connect you to other users ? not to share files this time, but to talk and chat with your friends.
Looks like this could be the year of VoIP (yeah I know that is every year, the same way every year is the year of Linux on the desktop).
Thanks to Phil for the link.