Good to have your company, Jeannette. There are many, many stores and websites that sell (or even give away) ebooks, other than B&N. You'll soon find them.
My own small independent is linked below. If you'd like to pick out two or three titles from our catalogue there (or give me an idea of your favourite genres), just drop me an email and I'd be delighted to send them as attachments in ePub for your Nook with our compliments for you to experiment with. I will talk you through the process for uploading to your device, too.
A handy tip is to download the excellent and free Calibre Library software here:
http://www.calibre-ebook.com. Thousands of us here at MobileRead and well over a million other ebook readers swear by it.
It offers many features. For instance, it will automatically catalogue and store your books (thousands if you collect that many) for upload to your Nook device any time and within a few seconds, it will instantly convert from one digital format to another if you like, and its 'Get Books' facility lists publishers and titles you can download -- even warning you when a title is locked by DRM software, which makes it difficult to share with family and friends and to use on devices other than your own.
Also, if you hit any snags, you'll find assistance and advice in the Nook-dedicated sub forum here by clicking on the little 'forums' button at the very top of this page and then scrolling down the short list to where your Nook is featured.
Hope this is of some help, Jeannette. Happy e-reading and very best wishes. Neil -- ntmarrATbewrite.net (but use the @ sign, of course)