Opensource SIP solution

http://flashphoner.com/html5-webrtc-phone-not-yet/
http://www-01.ibm.com/support/knowledgecenter/SSHR6W_8.5.5/com.ibm.websphere.wdt.doc/topics/tdevelopSIP.htm
https://github.com/DoubangoTelecom/sipml5
http://www.opensips.org/
http://www.voip-info.org/wiki/view/Open+Source+VOIP+Software
http://openmobilealliance.org/

http://kb.asipto.com/kamailio:skype-like-service-in-less-than-one-hour