The best kinds of traditions are sometimes the ones you make yourself, and Neil Gaiman has just come up with a winner.
It's called All Hallow's Read and the idea is that you celebrate Hallowe'en by giving someone a scary book. If you pop by the site you can see some lists of recommended books (the one I'm most curious about is Jim, Who Ran Away From His Nurse, and Was Eaten By a Lion by Hilaire Belloc which was recommended by Monica Edinger).
The last kids books I remember finding quite genuinely spooky were Joseph Delaney's series called The Spook's Books and I think I may have fallen a few books behind which should be rectified. I see from a quick visit to his site that your can now read the first of the series, The Spook's Apprentice, online for free. So there you are. My gift to you.
A few other quick links: you can watch or just listen to Neil Gaiman read The Graveyard Book in its entirety right here. And by visiting Book or Treat you can contribute to the Trick-or-Treat for UNICEF campaign. Just 75 cents could buy a child a book.