Welcome to the online JSON formatter at jsonformat.com. JSON is a data format that is gaining popularity and is used extensively in many AJAX powered Web 2.0 sites. Many websites that offer API's will return data in JSON format. Often the JSON provided has whitespace compressed to reduce the size of the data transferred. This site give you a quick and easy way to format the JSON so you can read it.
More info and links to useful JSON utilitiesjson.org - home of JSON. Detailed information on the data format.
Wikipedia - JSON - good description of JSON and Wikipedia
PHP from version 5.2 on has good support for JSON built in.
PHP 5.2 Jason - native support for JSON in PHP >= 5.2.
Python has a number of different libraries for JSON. Each have different strengths, a good comparison can be found at memerimon.com the creator of demjson
demjson - powerful and standards compliant.
simplejson - simple to use with no external dependencies.
Java json libraries.
org.json - implementation from json.org.
JSON Tools - LGPL implementation.
Microsoft C# json libraries.
Jayrock - LGPL version for Microsoft.Net Framework.