How to conference call/chat in Google Talk?

Conference Call

Open up a copy of google talk on all computers with which you wish to conference. After one copy is opened make a new shortcut for google talk but at the end of it add /nomutex. If you installed it to the default folder then your shortcut should read "C:\Program Files\Google\Google Talk\googletalk.exe" /nomutex. Open 2 instances of the software on every user's computer. After this start a chain: User 1 should connect on one instance to user 2. User 2 will connect on his second instance to user 3. User 3 will connect using his second instance back to user 1. With this chain everyone is connected to everyone.

Possible problems: Google will try to connect you with others on the same instance. To fix this just open a new instance. It seems that google will try to take calls on the newest IM client.

Note: You can also make a conference call with more people, just have need to have one less instance than the amount of people that exist.

Check with this link
http://lpahome.com/call.html

Conference Chat

Partychat is yet another means by which you can implement group chat facility on gTalk. Partychat allows you to create your own chat rooms, where others can join for a group conversation. For this, just add partychat@gmail.com as your buddy, create a chat room by sending the message ‘/create chatroom-name’.
Your friends can enter this chatroom by sending the message ‘/join chatroom-name’ to party@gmail.com .

For more details:
http://googlesystem.blogspot/.com/2007/09/chat-rooms-for- google-talk.html.