Skype is a software application that allows users to make voice and video calls and chats over the Internet. Calls to other users within the Skype service are free, while calls to both traditional landline telephones and mobile phones can be made for a fee using a debit-based user account system
Skype has 663 million registered users as of 2010
Most of the development team and 44% of the overall employees of Skype are situated in the offices of Tallinn and Tartu, Estonia
On 10 May 2011, Microsoft Corporation agreed to acquire Skype Communications, S.à r.l for US$8.5 billion
Wikipedia: Skype