I know it's a bit obvious, but this British classic offering weird tales-within-a-tale seems the obvious place to begin my very personal (i.e. totally unreasonable) survey of things to watch in the run up to the Spookiest Time of the Year. It's great fun and it can be found in its entirety on YouTube. Opinions vary on the different stories, but one thing is obvious - DoN set the template for many later portmanteau horror films from Amicus.
The last story, the ventriloquist's dummy, is truly disturbing and leads into the finale with its nightmare twist. Michael Redgrave is brilliant and the sheer violence (bloodless thought it may be) of the denouement is still disturbing. I'm surprised they were allowed to get away with it back in the days of powdered eggs and Mrs Mopp.
WARNING: This clip is essentially one humongous spoiler, but I couldn't find a better (i.e. less humongously spoilerish) one.