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.
Get in touch how and when you want to–over email, IM or a call.
Talk through your computer but hear your friends as if they were in the same room.
Your Gmail contacts are pre-loaded into Google Talk so inviting or talking to your friends is just a click away
Google Talk is in beta and requires a Gmail username and password.

Features

Instant messages: share quick thoughts in real time

Status updates: see if friends are around and what they are up to

File transfer: instantly send and receive files, pictures, and more

Free long distance: make PC-to-PC calls to people anywhere in the world

Audio conferencing: talk to multiple people at once

Gmail integration: chat with your friends on Gmail