Google Talk

"They say talk is cheap. Google thinks it should be free. Google Talk enables you to call or send instant messages to your friends for free -- anytime, anywhere in the world. Google Talk offers you:....

Google Talk is in beta and requires a Gmail username and password.
Don't have Gmail? Get an account using your mobile phone (US only)."
Ok, I did it at the request of a friend. I downloaded and installed Google Talk. It's neat how all your gmail contacts are automatically imported. I have 50 gmail account invitations left. email me and I'll give you one if you promise not to spam me :)