Working with .NET in a connected world your new favorite library should be Json.net. It just makes the world connect in an easy and REST-full way.
The developer of this library is Jason Newton-King, and he’s got a blog that shows you how easy it is to implement.
Not only should it be a natural part of your .NET project but it can also be used for iPhone/iPad development through MonoTouch . Here’s also a guide on how you do it. Hopefully it’ll transfer to MonoDroid when it becomes available.
Download Json.NET from here: http://json.codeplex.com/releases/view/50552