From Anthology of Ideas:
If you use future posts a lot also you probably find yourself looking back and forth from your post list to a calendar or recording your future posts on a calendar to avoid having a double post on a single day and then none for three days. On top of that there are the frequent “How many days are in March again” checks.
Well this plugin gets rid of all of that. It adds a simple month-by-month calendar that shows all the months you have future posts for (and the current month no matter what), it highlights the days you have posts for, and as an added bonus if you click a day the Post Timestamp boxes change to that day, month and year (although it doesn’t check the edit timestamp box to avoid accidental changes).
Also, see Working Ahead – Future Posts with WordPress for Lorelle’s tips on working with the future posts feature in WordPress.