Now that the System.Json API has been released (http://wcf.codeplex.com, http://wcf.codeplex.com/wikipage?title=WCF%20jQuery), I'll start posting a series of "improvements" that I've done over the past few months using that library. Let me know if you find it useful, and I'll bring it to the team to include in future releases of the Codeplex project.
To start, something simple: pretty printing. Like in Silverlight, when calling ToString() in a JsonValue object you get the JSON corresponding to the DOM. But in many cases, it's useful to have it pretty printed, for easier inspection or debugging. This is a simple extension method which accomplishes that.