This project implements a simple STUN server and client on Windows, Linux, and Solaris. The STUN protocol (Simple Traversal of UDP through NATs) is described in the IETF RFC 3489, available at http://www.ietf.org/rfc/rfc3489.txt
SIP Stack that is RFC 3261 compliant. Project has moved to http://www.resiprocate.org/
The Vovida Open Communication Application Library Polish (VOCAL-pl) is an open source project targeted at facilitating the adoption of VoIP in the marketplace. Localization for polish language.