JavaScript Object Notation (JSON) is simple, lightweight data-exchange format that is used by most AJAX implementations (although it can be used by other applications and domain spaces). It is used to serialize data structures into a text format that is especially easy to parse and evaluate directly from JavaScript code. Back in 2006, Atif Aziz approached me and asked if I'd like to coauthor an introductory article on JSON. The net result is the latest article on MSDN online, An Introduction to JavaScript Object Notation (JSON) in JavaScript and .NET.
The article focuses on JSON - its purpose, the standard, a comparison of XML and JavaScript, and so forth. The .NET examples use Atif's open-source Jayrock library, which provides classes for reading and writing JSON text as well as serializing and deserializing JSON to .NET types and vice-a-versa. It also includes support for JSON-RPC.
Enjoy!