Matej Kravjar

Plugin adds section to post edit page in WordPress admin, where the post metadata are displayed in convenient table with the option to export the data into JSON format

Post Meta View and Export

This plugin adds possibility to view and export post metadata for superadmins.

Automattic

Daniel Bachhuber

A quick and easy way to see post meta associated with any given post. When activated, this plugin prints your post meta keys and values inside of a post meta box.
Originally developed for <a href="http://vip.wordpress.com/" rel="nofollow ugc">WordPress.com VIP</a>-hosted clients, we thought it would be useful for development environments, etc. too. Feel free to <a href="https://github.com/Automattic/Post-Meta-Inspector" rel="nofollow ugc">fork the plugin in Github</a> and pull requests are always welcome. Hit us with feedback, questions, bug reports, and feature requests in the forums.

Post Meta Inspector

Lovely little tool. Saves having to go into the database and look through the postmeta table when debugging. Thanks!

Post Meta View and Export vs Post Meta Inspector