I always was worried about Skype closed-source code, but after reading this article about "NSA offering 'billions' for Skype eavesdrop solution", I became almost paranoid... Happilly there is nice and free open-source apps availiable, like Ekiga.Ekiga is an open source VoIP and video conferencing application, using H.323 and SIP protocols, suporting many audio and video codecs. You can read some good reviews here and here.
