Try books.google.com - choose a genre in the left sidebar, then click on 'public domain only.' You will find an extensive list of public domain books you can download to your Nook device.
Try freebookspot.com - this site has an extensive list of reference/textbook types. They are listed by subject. The fiction offerings are mainly science fiction and there quite a few of them. This is a reference goldmine for just about any other subject you can think of, including computers, internet, japanese, electrical engineering, finances, you name it.
Also look at fictionwise.com - in the left sidebar under 'Browse' click on 'free ebooks.'
There are more at free-ebooks.net - listed by subject, PDF format.
Read more: How to Find Free ebooks for Nook | eHow.com url://www.ehow.com/how_5780852_ebooks-nook.html#ixzz11wGROM7V