Skype
Company: Skype
"Qt has greatly helped us to bring Skype for Linux to users across various Linux desktops and distributions. It neatly integrates with the user's desktop theme and helps us provide a consistent, easy-to-use, yet powerful user interface that is central to Skype across all the platforms it runs on."
Skype is free and simple software that enables you to make free calls anywhere in the world in minutes. Skype, created by the people who brought you KaZaA, uses innovative P2P (peer-to-peer) technology to connect you with other Skype users. Skype is quick and easy to install, and does not require you to reconfigure your firewall or router. Just download it, register, and within minutes you can call your friends on Skype for free. Skype calls have excellent sound quality and are highly secure with end-to-end encryption. Now, you can also use Skype for conference calling with up to five people at the same time. There is no ad-ware or spy-ware.
For further information visit the Skype homepage.