VoipDiscount offers a simple tool for OS X to make cheap phone calls.
VoipGain provides you with the cheapest international calling rates available!
PowerVoip is the answer if you are looking for extremely international calls.
You can use EasyVoip in various ways to stay in touch at the lowest rates.
Note: The price of this software is a monthly charge.
conferencing (via VoIP and telephone
It provides a secure connectivity experience across PC and mobile devices.
over IP (VoIP) traffic
Spark is an open source, cross-platform instant messaging client for businesses.
group chats, VOIP, and strong
VoIP program which allows you to make phone calls over the internet.
Telephone is a VoIP program which
It works like a telephone to let you make calls through your computer.
almost any VoIP gateway provider
Analyzes network traffic of all connected devices.
SIP, RTP (VoIP) protocols...and RTP (VoIP). To cut
Provides a simple user interface for making VoIP calls with Asterisk PBX.
for making VoIP calls...open source VoIP PBX)