Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
AVOXI - AVOXI to deliver amazing call quality & an exceptional customer service experience.
MicroSIP - MicroSIP is a free portable SIP softphone for Windows based on PJSIP stack.
Sonetel - Sonetel is a communication app that lets you make an international business call at the cost of local calls.
Sipnetic - Sipnetic is a free VoIP softphone based on the SIP protocol.
Global Call Forwarding - Global Call Forwarding offers local and international toll free numbers which can be forwarded to any phone, anywhere in the world.