In addition, if you are wanting to catalog your hard-copy books, something like Goodreads or Library Thing is good for that (and you can keep track of the digital ones also, but it's not a manager like Calibre is). I also have a free android app on my phone called Book Catalogue which lets me scan barcodes and load them into a database. Goodreads has an app for that also. Sadly, I haven't found anything like this for Nook yet but I've only just begun to use a Nook and plan to quickly switch it to android anyway.
edit - forgot - no cameras on Nooks, so the barcode reader wouldn't be useful anyway.