Useful JSON Inspector & Visualizer – JSONmate
When working with JSON strings, it is usually hard too understand their hierarchy at the first look.
JSONmate is a web app that can beautify (and uglify) JSON strings where these strings can be directly pasted or loaded from a remote URL.
Also, it has a very nice visual editor for customizing the data and a visualizer that provides a different view for it.
JSONmate has support for JSONP too and it is an open source project.