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.
Ardesia helps you make colored free-hand annotations on your computer screen, record them, and share them on the network. You can use the tool to make effective on-screen presentations, highlight things, or point out things of interest. It facilitates online presentations and demos, showing in real time your computer screen to anyone in the network. You can use this tool to enhance your lessons or courses. You can create nice tutorials and documentation, saving the desktop images with your free hand annotations. It works with any pointing device. You can draw lines with different strength, select color, erase things, and draw arrows. You can free-hand draw geometrical shapes using the shape recognizer, insert text with the keyboard, and highlight screen areas. You can draw upon the desktop or select an image as a background.
Terminal Mixer allows sharing the stdin/out/err of a process through a Unix socket, TCP, or raw ethernet (the latter only on Linux). It allows sharing a pseudo-terminal as well, for terminal-aware applications. The users can be allowed only to watch, or even to contribute. You can run your favourite 'vim' or 'bash' and access it remotely, even with multiple users using them.
SpeexComm is a Speex-based, multi-platform voice communication engine meant mainly for gaming. Written in C99, the engine itself depends only on libc, but ALSA and Speex libraries are recommended for audio input/output and voice encoding/decoding. The engine is accompanied by some reference UIs.
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.
Sofia-SIP is a SIP user agent library, compliant with the IETF RFC3261 specification. It can be used as a building block for SIP client software for uses such as VoIP, IM, and many other real-time and person-to-person communication services. The primary target platform is GNU/Linux. Sofia-SIP is based on a SIP stack developed at the Nokia Research Center.