Andrew Norcross

tripflex

Creates a panel to change or delete meta keys in bulk. Useful for when you are switching plugins or themes that use specific meta keys for functionality, or for general cleanup for older sites that may have older meta data that is no longer in use.

Post Meta Manager

A simple utility plugin for changing or deleting post or user meta (custom fields) keys in bulk.

jphase

WP Modification History enables a metabox that shows modficiation history by date/time, user, and the values that were modified. The modified values are shown in a diff format so that you can easily see what lines and characters were modified, deleted, added, etc.
Within the settings page, you are able to toggle off/on meta values in the event you don’t want certain things to be tracked when hitting the update button on that post type.
Possible future features:
<ul>
<li>Additional settings and display options (AJAX pagination, limit of results per page/metabox, etc.)</li>
<li>Comments and remarks on a particular revision</li>
<li>Email notifications when specific changesets are made</li>
<li>Stats</li>
</ul>

WP Modification History

WordPress Modification History adds a metabox that shows modification history on a particular set of post types.

Post Meta Manager vs WP Modification History