We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
Nook Submission to Barnes and Nobles
I've looked at the Barnes and Nobles site and while it has lots of info on becoming a vendor for printed books, I don't see anything about how to submit an eBook.
My eBook is now on: http://www.lulu.com/spotlight/Stevej46
I is also available through the iBookstore now.
Since my book is Color photographs, I don't think submitting it for the Amazon Kindle is a good move right now since everything would only show in B&W. Hopefully Kindle introduces their Color Kindle soon.
I know lulu.com does something with eBooks for wider distribution once the book is on iTunes but how does that really work?