trixbox is an easy to install, VOIP phone system based on the Asterisk PBX. trixbox is designed for home or office use. trixboxs includes CentOS linux, SugarCRM, mysql, HUDlite, freePBX, and more.

2 Elastix

Elastix is an appliance software that integrates the best tools available for Asterisk-based PBXs into a easy-to-use interface. It also adds its own set of utilities to make it the best software package available for open source telephony.

3 CQiNet

Voice over IP (VoIP) software specifically for ham radio operators. The primary purpose is to use the Internet to link Ham repeaters with a secondary purpose of providing remote access for users. Compatibility with EchoLink and IRLP is a goal.

4 ICEcore

ICEcore leverages social software to unify team workspaces with real-time web conferencing. It's a collaboration platform for knowledge networking, program management, communities-of-practice, telework, and other business process and functional areas.