Lately I seem to have written my fair share of ghost stories. They aren't always meant to be scary. I don't think they need to be. Most of the ghosts in Dicken's A Christmas Carol weren't scary (with the possible exception of the ghost of Christmas future) and I think we could look to our Hollywood brethren and say quite a few of the specters on film are quite gentle (Can we look to Bruce Willis's portrayal in The Sixth Sense?)
That being said, I think that ghosts can be looked at in two ways, memories and ideas.
The ghost of memory is the one that we see most often, it is the spirit of grandpa Gino who throws the dinner plates across the room when the pasta isn't cooked properly. Most of Algeron Blackwood's stories are based on the ghost of memory.
The ghost of idea is a much harder one to nail down. It may have no reason to be there. It may have a fleeting association. It may only appear in the dream, locked away in our subconscious waiting for us to banish it and hoping it never does. This is the ghost that I would like to write about someday. The one that is much more psychological than metaphysical. I would like to think that The Shining is a good example of this story. We don't know the backstory, it just is, and it catches us at our most vulnerable.
What do you think? Are there other types of ghost stories that I don't know about?