I've been playing with the new SDK in Google Desktop Beta 3 and I've written a plugin that lets you have chat room style conferences with people in your GoogleTalk friends list.
So if you've got GoogleTalk and latest Google Desktop installed, and you'd like to chat with a group of your friends all at the same time, check out the GoogleTalk Conference Chat sidebar plugin.
It's currently in what I would describe as Beta, meaning I know there are things that need fixing but I'd like some feedback before I commit more time to the project. So please -- let me know what you think!
I currently support multiple chat rooms, next on the agenda is improved formatting and persisting chatrooms across sessions.