PBXware - PBXware is the world’s first and most mature IP PBX Professional Open Standards Turnkey Telephony Platform. Bicom Systems’ softswitch is offered in the Business, Call Center and Multi-Tenant Editions each supporting specific features.
freepbx - FreePBX is a web-based open source GUI that controls and manages Asterisk (PBX).
3CX Phone System - 3CXPhone is a free VoIP phone available for Windows, iPhone or any Android based smart phone such...
FusionPBX - FusionPBX is an open source FreeSWITCH GUI.
CommPeak PBX - CommPeak’s Hosted Cloud IP-PBX is a web-based highly customizable and feature-rich solution - the ideal, low-cost solution for an enterprise of all sizes.
Asterisk - An open source telephony switching and private branch exchange service for Linux.