Mark Jaquith

Some WordPress sites have problems with scheduled posts, where they don’t get published at the right time. Instead they appear as “missed schedule”. This plugin monitors scheduled posts, and makes sure that doesn’t happen.

Scheduled Post Guardian

Watches over scheduled posts, and makes sure they don't miss their scheduled time

Ron Zvagelsky

Monthly grid view calendar widget highlighting archived and/or future posts.
Additional Features:
<ul>
<li>Popup details for each date with posts</li>
<li>Optional details include post author and comment count.</li>
<li>Ability to show posts by post type, category, specific taxonomy and/or term</li>
</ul>
<a href="http://presshive.com/plugins/wordpress-blog-post-calendar-plugin" rel="nofollow ugc">For more information or to request additional features, please visit the plugin page</a>

Blog Post Calendar Widget

The Blog Posts Calendar Widget allows you to display your archived or future posts in a calendar as a sidebar widget.

Scheduled Post Guardian vs Blog Post Calendar Widget