In order to be able to use voice chat while in game, you need to install Teamspeak. You can download the client by
The server to connect to is ts.cracksmokingmonkeys.net.
We like to know what people's real names are, so it's preferable to enter your Teamspeak name as <in game nickname> - <real name>, although this is by no means required.
You can also see who is currently connected to the TeamSpeak server by clicking on the Live TS View link here or in the menu.