The GNU Gatekeeper is a free H.323 gatekeeper based on the OpenH323 project. You can use it to manage a Voice-over-IP network and let endpoints (e.g., Netmeeting) communicate through symbolic names. It also has an external interface for billing and other applications. It runs on a number of Unix versions (including Linux and Solaris) and Windows.
RAT is an RTP audio conferencing and streaming application that allows users to particpate in point-to-point and multi-point audio conferences over the Internet. Developing features include multiple sampling rates, mono/stereo, loss concealment, and IPv4/IPv6 support, and both versions feature encryption and run on a range of platforms.
Linphone is an audio and video Internet phone with GTK+ and console interfaces. It uses the SIP protocol, and is compatible with most SIP clients and gateways. It can use various audio and video codecs such as Speex, GSM, G711, G722, ilbc, amr, Theora, H263-1998, MPEG4, H264, VP8, and snow.
SCMxx is a console program that allows you to exchange certain types of data with mobile phones made by Siemens. Some of the data types that can be exchanged are logos, ring tones, vCalendars, vCards, phonebook entries, and SMS messages. It works with the following phones: S25, C35i, M35i, S35i, ME45, S45, SL45, M50, and probably some others, too. It basically uses the AT command set published by Siemens (with some other additional resources).
Bluel VMail is a semi-complete voicemail system that supports automated attendant, call transfer, e-mail delivery of voicemail messages, etc. It was designed to work with the Diamond SupraExpress ISA modem and Panasonic KX-T61610 hybrid phone switch (cheap!), but is probably portable to similar configurations.
OTRS is a platform independent Web-based help desk system that supports service organization of any kind (e.g. IT service, customer and technical product service, complaint management, public services, etc.) to increase their efficiency. It increases transparency as well as service quality and lowers your total cost of ownership. It has been certified ITIL V3 compatible by PinkVERIFY for incident, problem, change, service asset and configuration, request fulfillment, and knowledge management. Other ITIL processes like service catalog and service level management are supported as well.
NetUP UTM is a universal billing system for internet service providers of any size. Its modern approach to traffic accounting makes the system compatible with all popular platforms and network devices. Its key features include realtime traffic processing, Cisco Netflow and IP Accounting data collection, support for RADIUS authentication, and cross-platform compatibility. The core of the system is a smart and reliable accounting engine working directly with network equipment. It supports up to 100,000 users at a total speed of up to 3 Gbps. A flexible ratings engine and efficient administration tools make UTM a complete solution for IP/VoIP/WiFi/dial-up billing.