Tools
- JSONLint - The JSON Validator.
- SimpleJSON - Python Stuff.
- JSON Formatter (& Validator!)
- Tidy JSON - JSON Pretty Printer/Colorer - C#(.NET)
- Cerny.js - JSON Pretty Printing Demo
- jsonpretty(ruby)
Vim
- tidify a json in Vim
- JSON.vim - syntax.
- VIM - How to format and syntax highlight JSON file
- Add JSON syntax highlighting in Vim on OS X
