MoliUbiquity: JSON Tree
Please make sure you are using Firefox 3, with Ubiquity installed. Otherwise, nothing happen.
(For those are new to Ubiquity, you can visit its tutorial. Type about:ubiquity in your browser navigation bar to change your hot-key for triggering Ubiquity. Enjoy!)
=> 
json-tree: Show the selected JSON text (if not selected, then the text on the current page) in tree view.
preview: Show the pretty format of selected JSON text (if not selected, then the text on the current page).
execute: Show the selected JSON text (if not selected, then the text on the current page) in tree view, which can be expand or collapse, on a new tab page.
json-tree