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.
sms-queue handles an SMS queue for small networks or single user machines. It is designed for areas where many SMS messages are sent. It does not actually send the SMS itself, but instead calls an external application (depending on the SMS gateway you want to use) via a simple standard interface. The communication between client and server is based on a simple ASCII protocol over TCP/IP which should make it easy to develop your own frontend.
Wammu is a mobile phone manager that uses Gammu as its backend. It works with any phone that Gammu supports, including many models from Nokia, Siemens, and Alcatel. It has complete support (read, edit, delete, copy) for contacts, todo, and calendar. It can read, save, and send SMS. It includes an SMS composer for multi-part SMS messages, and it can display SMS messages that include pictures. Currently, only text and predefined bitmaps or sounds can be edited in the SMS composer. It can export messages to an IMAP4 server (or other email storage).
QuteCom (formerly WengoPhone) is a multi-platform VoIP client. The GUI is Qt-based, and the Video-over-IP engine is based on the eXosip, oSIP, oRTP, ffmpeg, and libgaim projects. The eXosip module is extended by a phApi module, which implements a high-level, easy-to-use call control API. It supports PC-to-PC voice, video, and chat. One can use a standard SIP service provider such as Wengo to be assigned an incoming number, make calls to PSTN/cell phones, get voice mail, and more. In addition to SIP/SIMPLE QuteCom provides IM functionality using libgaim, so it is compatible with all protocols supported by libgaim.
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.
Baudline is a time-frequency browser designed for scientific visualization of the spectral domain. Signal analysis is performed by Fourier, correlation, and raster transforms that create colorful spectrograms with vibrant detail. Conduct test and measurement experiments with the built in function generator, or play back audio files with a multitude of effects and filters. The baudline signal analyzer combines fast digital signal processing, versatile high speed displays, and continuous capture tools for hunting down and studying elusive signal characteristics.
oRTP is a library implementing the Real-time Transport Protocol (RFC3550), written in C. It is easy to use and provides a packet scheduler for sending and receiving packets on time, adaptive jitter compensation, automatic sending of RTCP compound packets, and the RTCP parser API. It works with IPv6.