tSIP - tomeko.net/software: SIP client for Windows.
MicroSIP - MicroSIP is a free portable SIP softphone for Windows based on PJSIP stack.
CommPeak PBX - CommPeak’s Hosted Cloud IP-PBX is a web-based highly customizable and feature-rich solution - the ideal, low-cost solution for an enterprise of all sizes.
Linphone - Linphone is an internet phone or Voice Over IP phone (VoIP).
Acrobits Softphone - Acrobits Softphone, an app for entry into the world of SIP.
3CX Phone System - 3CXPhone is a free VoIP phone available for Windows, iPhone or any Android based smart phone such...