Welcome to MR, dbarthel
If you mean Public Domain ebooks, MR has a large library of these. They have been carefully handcrafted by some very dedicated MR members. I'm not familiar with the Nook, but I believe it will read non DRM'd ePubs. (
MR's ePub library listings)
Have you tried
feedbooks.com ....
manybooks.net ....
or smashwords (free and for purchase)?
You can also check my signature for a listing of a few of MR member authors. Click on the feedbook link and it will take you to a list of those authors. You can check some of the names in my signature under smashwords for those MR author members at smashwords also.
Enjoy exploring the forums and congratulations on your Nook.