RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
letsBrik - A Skype Alternative that is entirely web browser based.
Dialpad - Switch is a cloud-based phone system built for Google Apps users.
Amivox - Would you like to make international calls either free or at local rates ?
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs
KeepCalling - Best Rates for International Calls. No Contract, Expiry, or PIN. Use Any Phone, Smartphone or PC.