As you know, because you are such a FAITHFUL reader of this blog, there is new JSON support on WCF for version 3.5. The way you get JSON though, would be only through a service interface. But what if, for whatever reason, you cannot use .NET 3.5 (like maybe the corp standard where you work is still on .NET 3.0), but you still want to play with JSON on the wire.
Now there's a easy-to-use standalone JSON library for .NET on CodePlex.
Check it out!