Linphone.org
Counterpath.com
Zoiper.com
Counterpath.net
Wengo.com
Pjsip.org
Openvbx.org
Iptel.org
Asterisk2billing.org
Opus-codec.org
Askozia.com
Sipfoundry.org
Asterisk.org
Elastix.org
Freeswitch.org
Jitsi.org
Ekiga.org
Kolmisoft.com
Opensips.org
Asteriskwin32.com
Kamailio.org
Mumble.com
Vmukti.com
Speex.org
Vicidial.com
Comtube.com
Asterisk-france.org
Incontact.com
Voipcallrecording.com
4psa.com
Echolink.org
51callcenter.com
Multi-skype-launcher.com
Drogon.net
Globe7.com
Voipbuster.com
Fring.com
Icall.com
Pamela.biz
Voxox.com
Voicent.com
Prettymay.net
Portsip.com
Mizu-voip.com
Openimscore.org
Sipdroid.org
Starfish-pbx.org
Villagetelco.org
Cosmocommerce.com
Pc-telephone.com