I just added a Mumble server as well... I'm not completely sold on it yet, but it has several very cool features.
- Open Source Software
- ALL traffic is encrypted via SSL
- Data is encrypted with AES256
- Voice is encrypted with AES128
- Native Windows and Linux Clients
- Linux Client uses ALSA (TeamSpeak uses OSS)
- Text to Speech like Ventrilo
- Comprehensive mic setup (something that TeamSpeak lacks)
- No connection limits (the free Ventrilo license limits you to 8 connections)
- Better channel hierarchy
- Some other things I can't remember at the moment
Like I said, I'm not completely sold on it yet. It's not quite as polished or user friendly as TeamSpeak or Ventrilo. I'm going to run it in parallel with TeamSpeak so people can poke at it. If people feel strongly about TeamSpeak or Mumble one way or another we can switch.
http://mumble.sourceforge.net/
Connect to it at games.sleepysheep.org as well.