MeetingMogul - Join any conference call with one-touch
Dialpad - Switch is a cloud-based phone system built for Google Apps users.
CALLR - CALLR is an extremely helpful app for those who have to deal with call control protocols for their business. You can create a customized call control system that will perform a wide range of functions.
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs
MobileDay - MobileDay provides one-touch access into conference calls and online meetings from iOS or Android devices.
3CX - Hosted PBX with CRM integration and mobile apps