An Introduction to JavaScript Object Notation (JSON) in JavaScript and .NET:

* Jayrock is open-source, making it possible to extend or customize as needed.
* ... While ASP.NET AJAX includes some support for creating and parsing JSON text, its primary purpose is to offer a rich platform for building end-to-end Ajax-style web applications in ASP.NET. The extra bells and whistles can be distracting when your main focus is JSON.

That's the kind of attitude I like to see. So much stuff is overkill, like XML for AJAX.

EDIT: Also good -- The comments in json2.js, a reference impl for JSON here.

// Due to a specification blunder in ECMAScript, typeof null is 'object',
// so watch out for that case.