I know that it’s not go much to do with Chelsea but I spent a couple of fascinating days at the Garden Museum listening to Joshua David, Robert Hammond and Piet Oudolf talking about the High Line. It was incredibly inspirational and makes you realise what a few individuals can do in the face of considerable public and government resistance. The result is amazing and must be on your list of places to visit if you are going to New York. Here is a link to the Garden Museum website but there is lots of stuff on the internet about it.
There was also a really good article in the Telegraph on Saturday about it.
The Landscape Institute has run a competition to find similar ideas for London. The short list of 20 are on display at the Museum.
ps. I am a Trustee of the Garden Museum – so I am a bit biased, but I assure you it was wonderful.