RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
freepbx - FreePBX is a web-based open source GUI that controls and manages Asterisk (PBX).
MyOperator - MyOperator is a cloud-based call management system for voice communication purposes.
Wazo - Wazo is a unified communications platform based on Asterisk and focused on extensibility.
Asterisk - An open source telephony switching and private branch exchange service for Linux.
FreeSWITCH - FreeSWITCH is an open-source media application designed to support popular protools such as SIP and WebRTC and provides a platform to develop voice and video applications.