Originally Posted by nyrath
Calibre can also convert ebooks in a variety of formats into epubs that the Nook can use.
I am unsure if there is a way to have Calibre wirelessly load books onto your Nook. I usually just plug my Nook into my computer. On Calibre, it will tag all the books in your library that are also on your Nook with a blue check-mark. Books you want to add to your Nook can be selected, and sent by pushing a simple button.
Note that on your Nook, there are two "libraries." One is of official Barnes & Noble books you've purchased. The other is your own documents library, containing ebooks you've manually added to your Nook.
No, you cannot load books wirelessly onto the nook through Calibre. You have to connect the nook to the computer via USB, then you can, through Calibre, move the books onto the device. The books will show up in 'My Documents' library (not the B&N library).