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
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
ConvertOnline.IO - Free online tools to convert between various data formats including Javascript, YAML, JSON, HTTP Query String and more. Friendly online tools for URL decoding and encoding
JSONedit - JSON editor for Windows and Wine with tree, list and text views.
FreeFormatter - Freeformatter is a platform that contains free online tools for developers, including formatters (json, html, xml, sql, etc.), minifiers (css, javascript), compactors, validators, and much more.