JSONLint - JSON Lint is a web based validator and reformatter for JSON, a lightweight data-interchange format.
JSON Editor Online - View, edit and format JSON online
JSONFormatter.org - Online JSON Formatter and JSON Validator will format JSON data, and helps to validate, convert JSON to XML, JSON to CSV. Save and Share JSON
Code Beautify JSON Validator - Code Beauty’s JSON Validator or JSON Lint is easy to use tool to copy, paste and validate JSON data.
JSONedit - JSON editor for Windows and Wine with tree, list and text views.