Social Source Commons

Free IP PBX / SIP server supports set-up of professional phone systems that allow you to create extensions, transfer calls, and extend VOIP services to all users. Works via your computer network (no separate phone wiring) and allows use of SIP software phones on your PC or any SIP hardware phone.

The FreeSWITCH project is building an open source softswitch, which will be optimized for high definition voice.