We started with Mumble server but moved to TeamSpeak because it is more feature-rich. I have the website now able to link your TeamSpeak/Steam/Forum accounts and am working on an interface where we can create "events" (in-houses, all mid days, other games, whatever) and you will earn "points" for attending those events.

TeamSpeak's serverquery let me do a lot of cool things easier than Mumble/ice. There is a TeamSpeak client for linux (http://www.teamspeak.com/?page=downloads)!