I know this isn't a folk song per se, but I like having poems mixed in with my repertoire sometimes. Good ones that come immediately to mind are the Raven, by Edgar Allen Poe, and The Cremation of Sam McGee, by Robert Service.

One poem that is on my 'to learn' list is the Goethe poem, Die Erlkonig (the Elf King.) It would work very well at this time of year. It is about a father who loses his young son to a faerie king.