Loudtalks Lite - Push to Talk PTT VOIP

extract-loudtalks-to-your-flashdriveLoudtalks Lite is a Free Portable Tool that supports Push to Talk (PTT) Voice Over IP (VOIP) communication. It functions similar to popular software like Skype.

Phoner Lite - VOIP

phoner-lite-free-internet-phonePhoner Lite is a Portable VOIP (Voice Over IP) or Internet Phone that can be used to "make phone calls using your computer" enabling you to establish Voice over IP communication with your friends, colleagues, clients and more. Phoner Lite is Freeware and shares the same basic code as Phoner, however utilizes a different GUI.

PicoPhone - Free VOIP Internet Phone

picophone-free-voipPicoPhone is a Free VOIP Internet Phone application with chat. The author created PicoPhone because most Internet phones use overly complex protocols that can cause problems when used with NAPT routers.