Wikipedia
Deltathree
Deltathree Inc. is an American company engaged in the business of voice over IP telephony services. The company was one of the first in the world to offer a telephony service over the internet.
Users can either use the free softdialer product and make calls through their PC, or sign up for the broadband phone service and receive an Analog Telephony Adapter (ATA)or the linksys PAP2 device. Both devices allows users to plug a standard phone into their internet connection and make calls independent of the PC.