PartyChat adds one of the many missing features from Google Talk: chat rooms. You need to add partychat@gmail.com as a friend and use commands to create a room or join an existing one. To make sure nobody joins your room accidentally, password-protect it.
PartyChat is like a group chat, except that it's less obtrusive and persistent across different login sessions.
For example, say your friends are in a party chat named "drivel". To enter the chat, IM partychat@gmail.com with the line "/enter drivel." After that, you'll receive messages sent in "drivel" from partychat@gmail.com and all messages you send to partychat@gmail.com will be broadcasted to your friends in "drivel."
If you log out of Google Talk and then log back in, you're still in the party chats you were in prior to logging out. To leave a party chat, IM "/leave" or "/exit" to the address you were chatting with (e.g. partychat@gmail.com).
Only Google Talk's gadget has an option for group chats, while PartyChat can be used in Gmail Chat, the desktop client or any other Jabber client.
Some useful commands:
/create chat_name [optional_password] - creates a new party chat. If you provide a password, then other users must give this password to enter the chat.
/join chat_name [password] - join an existing party chat. If the chat has a password, you must give the password to enter.
/alias [name] - give yourself an alias; if you do not specify a name, your current alias is removed
/commands - displays the list of commands
For more details: http://googlesystem.blogspot.com/2007/09/chat-rooms-for-google-talk.html
How to conference call in GTalk ?
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