Java wrapper for the popular chat & VOIP service
A beautiful SMS messenger for Android
Java VoIP Softphone (SIP) (replaced by jfPhone)
Accent interfaces and controls systems through goals and policies
SIP Video Multiconference Media Server with WebRTC support.
Cress is a comprehensive toolset for graphical service/workflow design
Java VoIP/SIP PBX system (replaced by jfPBX)
Positional Audio Communication for Minecraft with Mumble
The OZEKI VoIP Service Checker allows you to check VoIP services.
C++ SIP stack based on Chrome source code