Issabel PBX - Unified Communications
VICIdial Contact Center Suite
VoIP/SIP SoftPhone (formerly known as jphonelite)
Unified Communications System - PBX System
Java VoIP Softphone (SIP) (replaced by jfPhone)
Accent interfaces and controls systems through goals and policies
Enterprise telephony recording and retrieval system
Cress is a comprehensive toolset for graphical service/workflow design
A simple noise gate app intended for use with VOIPs like Skype.
This project has been relocated to http://github.com/sippy/rtpproxy h