Skype

Features:
* Unlimited free high-quality worldwide voice communications
* Superior sound quality (better than your regular phone)
* Works with all firewall, NAT (Network Address Translation) and routers (nothing to configure)
* Friends list shows you when your Skype friends are online and ready to talk or chat
* Your calls are encrypted end-to-end for superior privacy
* Based on cutting edge P2P technology

Download:

http://rapidshare.com/files/24503891/SkypeSetup.exe

or
http://www.skype.com