Google has launched Group Chat feature just like Yahoo's Conference..
To start a group chat, launch the Google Talk Gadget here, and start a chat with one of your friends. Click on the button at the top of the chat window that says "Group Chat," and then pick the name of the third (or fourth, or fifth...) friend you want to invite from the drop-down menu. They'll receive an invitation to join the group chat. If your friends are using Gmail chat or the Google Talk client, their invitation will launch the Google Talk Gadget.