If you are attempting to write a Iphone application to talk to a webservice, JSON is one of the best ways to go. Now unfortunately there is no native support in the Iphone SDK for JSON. There is a project called json-framework that provides a framework called json-framework.
There is little documentation on how to install it though. Recently I found a news group posting on how to do it along with a dmg! I have mirrored the dmg file just in case it gets removed from that posting.
So here are some instructions on how to install it.
I have also mirrored their test application they built in the news group post. So if you download that and make the project changes there, you should be able to compile touchJSON into your application.