4PSA VoipNow is PBX software for service providers and enterprises. Easy to use and deploy, it can run on x86 or PowerPC based servers and delivers advanced IP telephony services. It can be deployed in various working scenarios to provide hosted VoIP services in high availability xSP environments, advanced call center services, or enterprise telephony in organizations of all sizes. A free Express version is available.
AgileVoice provides features for running VoIP businesses, including broadband residential and business phone, PC to phone, wholesale (termination/origination), traffic exchange, IP centrex, calling cards, and more. It was designed with carrier grade customers in mind. As such, it scales from many Asterisk systems down to a single all-in-one system.
Amatix Office is a complete communication platform for small and medium-sized businesses. It provides email, calendar, contacts, conventional telephony like ISDN, new generation VoIP telephony like SIP, instant messaging, presence, and other features needed to power a business. Amatix Office is very easy to install and use and does not require any special IT skills. It is a live software appliance which boots a computer directly from a CD or USB flash drive without any software installation.