Because on this site I generally stick with books I personally do or might find interesting, I've created something of a sister site that just lists all the upcoming books I can find and organizes them in descending order of pub date. You can also browse by month. For lack of a more inspiring title, I've called it Upcoming American Civil War Books. It's not even close to being up to date yet (esp. for the Fall 2010 months) but should be within the next week or so. There is also a blog roll link for it so check back often. Hopefully, you will find it of use.
BTW, feel free to email me with suggestions (preferably with a URL for the book) if you know of one that isn't listed.