Previously mentioned Google Talk Gadget has integrated a new Group Chat feature for your Google Talk contacts.
To use Group Chat, just start a conversation with a contact, then click the drop-down on the right of the chat window and select Group Chat. From there you can add as many contacts as you want. Granted, the idea of Group Chat is far from innovative (a lot of GTalk users have wanted this for sometime), but it's nice to finally see it rolling out. Group chat is currently only available with the Google Talk Gadget. Thanks Mike!