HEATKEYS

3CX VOIP PBX - provides an easy to use, plug and play SIP - IP PABX for Windows. With a software based IP PBX you will save on PBX maintenance and halve your phone bill. Download the FREE edition today and break free from your proprietary phone syste...

Office SIP Server is free VoIP and Instant Messaging Software

Linphone, Free SIP VOIP client, open-source voip software for Linux, windows, mac, iphone, android. Free sip voip sdk.

The Award Winning Business Phone Service over the Internet. OnSIP business VoIP service is a hosted pbx system that allows you to streamline your business communications. There’s no phone company hassle, no phone system to buy or manage, no contracts

ENUM registration

Welcome to voip.about.com, your guide site to everything Voice Over IP, also called VoIP, IP Telephony or Internet Telephony. Learn how to make free or cheap local and international calls using your PC or phone. Stay updated on VoIP hows and whats, V...

Internet Telephony

SIP Hosted PBX, Multi-Tenant, VoIP Platform for Service Providers - provides scalable and reliable SaaS IP Telephony Platform. Based on the Session Initiation Protocol (SIP), the Brekeke products provide robust SIP Communication Platform for Service ...

Open Source SIP Server - Kamailio (former OpenSER)