Skype is software that enables you to make free calls anywhere in the world. Skype uses innovative P2P (peer-to-peer) technology to connect you with other users. It offers several features, including SkypeOut calling from Skype to regular and mobile phones worldwide, conference calling, and secure file transferring. Skype calls have better sound quality than your regular phone and are highly secure, with end-to-end encryption.
Version 2.5 offers improved calling, free calls to phones within the US and Canada until the end of 2006, the ability to send SMS messages, and new Outlook compatibility.