TeamSpeak 3 is the most advanced voice communication technology for games and communities currently available. The high quality connection ensures crystal-clear voice communication. With the integrated file sharing, the powerful permission system and minimal performance footprint on your PC, TeamSpeak 3 is the best available VoIP program available.
Mumble is the open source alternative for voice server. The simple user interface and integrated in-game overlay makes the program popular amongst gamers. And since it is open source no licence has be paid, making Mumble the cheapest voice server technology available.