Greg Ross

Adds a JavaScript calendar to the scheduled publish widget to allow you to select a date and time graphically instead of via the text entry boxes.
This plugin uses the gpl’d dhtmlxcalendar (http://dhtmlx.com/docs/products/dhtmlxCalendar/index.shtml) for the calendar control.
This code is released under the GPL v2, see license.txt for details.
<h3>Roadmap</h3>
<ul>
<li>None at this time.</li>
</ul>

Schedule Posts Calendar

Adds a JavaScript calendar to the scheduled publish widget to allow you to select a date and time graphically instead of via the text entry boxes.

timlinden

Remembering to post every day, and which days you already posted, is super easy with this plugin. 
It shows you a calendar with days red when there isn’t a post, and days green when there is. Green 
days you can hover over and see the title of the post, and click to edit the post for that day.

wpFutureCal

A simple calendar that displays when you edit posts, showing which days you have posted on.

Schedule Posts Calendar vs wpFutureCal