Viber - Free and secure calls and messages to anyone, anywhere. Keep your conversations going no matter where you are.
freepbx - FreePBX is a web-based open source GUI that controls and manages Asterisk (PBX).
MiVoice Business - MiVoice Business is a business communication platform that delivers voice, messaging, mobility, presence, conferencing, collaboration and applications.
Asterisk - An open source telephony switching and private branch exchange service for Linux.
Screenleap - Screenleap is a web app that lets users share their device's screen over the Internet. These screens can be a desktop computer monitor or a smartphone screen or anything else that can load a web browser. Read more about Screenleap.
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.