Not really lending, but nothing stops you from just sending a copy to someone. Most classic books (aside from some exceptional hogs like Les Misérables, War and Peace or Don Quixote) are small enough to easily email.
No way to do it through the B&N servers or B&N lendme program, because B&N doesn't even really see sideloaded content on your Nook.
I don't know about epubbooks.com, but PG eBooks are DRM free as well as cost free. While you could easily email a copy of the eBook to your friend, it may be simpler for them to just go to gutenberg.org themselves.