Popular high-performance JSON framework for .NET
* Flexible JSON serializer for converting between .NET objects and JSON
* LINQ to JSON for manually reading and writing JSON
* High performance, faster than .NET's built-in JSON serializers
* Write indented, easy to read JSON
* Convert JSON to and from XML
* Supports .NET 2, .NET 3.5, .NET 4, .NET 4.5, Silverlight, Windows Phone and
  Windows 8 Store

The JSON serializer in Json.NET is a good choice when the JSON you are reading
or writing maps closely to a .NET class.

WWW: http://james.newtonking.com/json