The Taridium ipbx is a complete software-based VoIP PBX system that replaces a traditional proprietary hardware PBX. It runs on Linux without the need for extra software licenses, and is based on the SIP standard. It supports many phones and is available for free in a 5 user version.
Gemeinschaft is a PBX based on Asterisk, MySQL, Apache, and PHP, and designed for high availability and clustering. It provides automatic provisioning for mass deployment, and can handle over 10,000 users. Administration is done via shell scripts or a Web GUI. Hot-desking and mobility are supported. German voice prompts are included. There is a standards-compliant Web GUI with internationalization (and German and English translations). Outbound and inbound routing with full PCRE support is included.
Kablink Teaming (formerly ICEcore) is a collaboration platform that includes everything an enterprise needs to handle team coordination. It provides teams with real-time communication using IM, conferencing, and application sharing, as well as document sharing and content management features that allow organizations to create project teams and share content amongst team participants. Users can create a wiki or blog for a particular project and have it available to anyone in the company. It also features searching, a Web form builder, version and author history, and more. It includes a workflow engine that allows custom business processes to be implemented.
Sipcat is a software IP telephony system that helps businesses increase productivity and reduce telecommunication costs. It allows you to start running your own voice over IP PBX in a matter of minutes. It contains a complete Linux distribution, including Asterisk and all required 3rd party software.
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.