I just saw this thread and thought I would post about my own experiences. In my old house, I would wake up in the middle of the night to my bed shaking violently on its own. And I mean violently. And no, we didn't live on a fault line, and the house was pretty sturdy. Other than that I would hear footsteps around my room and breathing in my ear, and all three of these things have stopped since we moved.
Although the most solid evidence I have that ghosts exist is the experience in my friend's house. He had a wind up music box, which he had never wound, and yet it would start and stop playing all on its own. I was sitting next to it when it started, and I studied it and there was nothing strange about it, it was just a standard old music box.
But yea, those are my experiences, and I do believe that a strong energy can leave behind an imprint, and we can experience it as a paranormal encounter. Saying I believe in ghosts might be a stretch, per se, but there are undeniably things that can't be explained via standard reasoning, so I guess it would be better to say I believe in the paranormal.