Didn't catch all of the references in Guillermo Del Toro's amazingly comprehensive Treehouse of Horror intro for The Simpsons? These folks think they did. (Though there are a few more in the comments.)
The people over at MoviePilot put together this video, which pauses and labels each of the horror references in the intro sequence—including a bunch of callbacks to previous Treehouse of Horror segments. Give it a watch and see if you can spot anything they missed.