We start with an app dedicated to the most popular social network and its application for Windows Phone 7, the app is free on the Marketplace and a graphic and an 'interface and navigation lines resume the operating system. Fortunately, application updates are frequent, there are many users who complain about some minor bug or some feature not yet implemented fully in the application than the browser version, however, to use Facebook for Windows mobile Phone 7, this is the official application, which in general works reasonably well and allows use of basic social network.
WhatsApp is also an application for Windows Phone 7 which allows a completely free chat messaging between devices with WhatsApp installed, a kind of Skype if you will, that can remain in the background waiting for messages: just make arrangements with your friends , and you can install it for free unlimited texting. Be aware though that is obviously required an internet connection to operate, in particular the app for Windows Phone 7 is excellent, with lines and designs that reflect the operating system. It seamlessly integrates into the system, to exchange pictures and is also completely free.