I do, very much so but ghost is such a generic term. I believe it is a spirit if you will from a person who has business to finish or feels their presence can offer comfort to those they leave behind.
In my case I had a visit from my grandpa Hawk when he passed. My mom says I was dreaming but to this day I tell you I was as awake then as I am this moment. He came to me to let me know it is okay, he was okay. That he loved us that it was okay that he was gone because he no longer was in pain or suffering. Next day during the funeral my cousin and I who were both close to this grandpa were in good spirits. Our parents were not happy that we were laughing and smiling during the service, we were being disrespectful and not honoring our grandfathers memory. We were because I wasn't the only one he spoke to that night to say it was okay, he is okay.
I'm of the opinion just because I can't explain it or touch it or take a picture of it, it doesn't mean it isn't there. Same with UFO's, big foot and Loch Ness. Just because there isn't defenitive proof and I haven't seen it doesn't mean they don't exist. New speices are being found every year that people thought were dead or didn't know exsist.
But i'm all for everyone having their own beliefs. Oh and I believe that the husband of the former owner of our house is still here and makes his presence known from time to time. More when we first moved here, but now still from time to time.