Post Status Scheduler allows for scheduling of post status changes, category/tag adding or removing and 
removing of postmeta on any given date or time. It can be activated on any post type and shows 
up on the post edit screen in the publish section. From version 1.0.0 it has a feature for sending 
an email notification to the post author on the scheduled update.
<h4>Shortcodes</h4>
<ul>
<li>[pss_scheduled_time post_id=””] can be used to get the post’s scheduled date and time.</li>
</ul>
<h4>Filters</h4>
Scheduled Update: 
* post_status_scheduler_before_execution 
* post_status_scheduler_after_execution
Email Notification ( version 1.0.0 ): 
* post_status_scheduler_email_notification_recipient_email 
* post_status_scheduler_email_notification_subject 
* post_status_scheduler_email_notification_date 
* post_status_scheduler_email_notification_body

Post Status Scheduler

Change status, categories/tags or postmeta of any post type at a scheduled timestamp.

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 Status Scheduler vs WP Modification History