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.
HylaFAX is a fax and paging system for Unix. It supports sending facsimile, receiving facsimile, polled retrieval of facsimile, transparent shared data use of the modem and sending alpha-numeric pages. The software is structured around a client-server architecture. Fax modems may reside on a single machine on a network and clients can submit outbound jobs from any machine that can communicate with the machine on which the modems reside. An access control mechanism is included to control which users on which machines may access a server.
HERMESfax is a fax document management system that offers simple workflows and feature-rich possibilities. Features include sending and receiving faxes, forwarding faxes between users, management of user documents, workflow management, and supervising the service. It is a Web-based application offering: persistence of historical documents in an SQL database (MySQL and PostgreSQL), filesystem load balancing, multi-user access, privacy and security of documents, and hierarchical management of workflows.