VICIdial Contact Center Suite
Cellular manager for mobile phones/modems
Web based system for Computer Assisted Telephone Interviewing (CATI)
A WebRTC-Enabled Chrome Extension for Seamless Call Center
Software per Call Center
Unified Communications Server
Enterprise telephony recording and retrieval system
Multi user address book application accessable through the web.
Cress is a comprehensive toolset for graphical service/workflow design
A command line utility for remote controlling Polycom VVX IP phones
Java VoIP/SIP PBX system (replaced by jfPBX)
JAvascript Voicexml InterpretER
A simple noise gate app intended for use with VOIPs like Skype.
GNU Telephony Services and Applications
1 on 1 Webcam Videochat Script with P2P Support