Mumble is our choice for VoIP. It is completely open-source and free. It is comparable to other popular programs like Ventrilo, TeamSpeak, or Roger Wilco. It features high quality, low latency voice processing and many other features that the others don't.
Download Mumble here:
http://mumble.sourceforge.net/
Then just
click here to connect!
Link doesn't work? Here's our IP and port...
IP: mumble.noxiousnet.com
Port: 64738