Linphone - Linphone is an internet phone or Voice Over IP phone (VoIP).
RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs
Sipdroid - Free and open-source SIP/VoIP Client
Nextiva - Business VoIP, cloud phone systems trusted by more than 150,000 companies. Powered by the leading cloud PBX VoIP platform, Nextiva is rated the best business VoIP service provider.