Halloween is tomorrow. If you won't be out in costume, and you want to sit at home (while dressed in costume) and watch something... um... festive(?) of course Netflix, Amazon Prime and Redbox have quite a few options available.
You could just browse the horror genre on their websites just like you would any other day, but Netflix has "decorated" their site with a dedicated Halloween Favorites list for you to browse through (they know me so well).
Might I suggest Ghostbusters, The Evil Dead, Cabin in the Woods, and a film I was pleasantly surprised by from 2006 by Korean Director Joon-ho Bong, The Host. There is also one of my favorite Tim Burton films: Nightmare Before Christmas, which is that film I always watch around this time that helps me transition from Halloween mode into Christmas mode.
And in case you're feeling really adventurous there are two silent classics that have inspired many: Nosferatu, and The Cabinet of Dr. Caligari.