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WordPress.org API's is a set of API's on WordPress.org web site.
Secret key generator for wp-config.php.
Stats about the systems websites are running WordPress on.
WordPress Version Checker.
Details about the various individuals who contribute to the WordPress code base. Used in Credits Screen.
List of popular import plugins in the WordPress Plugin Directory used by Tools → Import Screen.
Note: Some docs on this api can be found here: http://dd32.id.au/projects/wordpressorg-plugin-information-api-docs/