This happened to my mother when she was a young girl living with her family in an old house in St. Alban's, Vermont. The house was over 100 years old at the time.
My mother and her sister Michelle slept in the basement which had been converted into a bedroom for them. They had twin beds that were positioned against the same wall and, from where they slept, they could see directly across to the stairs leading up into the kichen. My mother says that many nights she woke up feeling "like there was something there" and she'd look into the stairwell to see a smokey blackish apparition floating there in the doorway. At times she said it looked vaguely human and other times it was kind of "blobbish;" and sometimes, she would see it turn slowly and it would go up the stairs and vanish.
Being only 10 or so, she'd get scared and cover her head with the covers when she saw it. She'd peek out every once in a while until she didn't see it anymore and then she'd do something I don't think I would have had the guts to do... she'd run up the very stairs that she saw the thing on to go sleep at the foot of her parents' bed. Why she'd want to go near where she just saw something so freaky I'll never understand.
She never told anyone about the ghost. She said she'd tried explaining to her parents once when it first started happening and they found her at the foot of the bed, but they dismissed the ghost story and chalked it up to a child's imagination. They never asked her again and she knew they didn't believe her anyway. She'd just end up in their bed every once in awhile and nobody thought much of it, but it happened frequently and my mom was witness to it many times before they eventually moved out of the house.
Well, one summer, my Aunt Michelle, who used to share that room with my mother, came to visit. We got on the subject of the paranormal, and I could tell mom wanted to talk about her experiences in the St. Alban's house. But before she got a chance to speak, my aunt asked my mother if she remembered the house in Vermont. She asked, "Did you ever see anything strange in the stairway down in that basement?" My mom said she instantly got goose bumps and felt like crying. One, for having validation that it wasn't only her who saw the ghost and two, because it was just too creepy a revelation. My aunt said it never really scared her, but that she'd see it from time to time. (Michelle was a lot younger than my mother.) They both agreed that, looking back, they felt the spirit was just watching over them and generally harmless.
The following year, my Uncle John confessed to having seen something in the stairway as well. He was up early one morning and, being the bratty little brother that he was, he planned on going downstairs to wake my mother and aunt up by jumping on them and being a pain. But he said that as he turned the corner and started down the stairs, he saw that black shadowy thing and skidded to a stop, turned around, and went right back to his room. He also never told anyone until that day but spoke very matter of factly, about seeing it.
This apparition/shadow person ghost story is compelling for two reasons. First of all, it nicely correlates the idea that shadow ghosts can morph into apparitions, revealing that dark shadows are ghosts of people. Secondly, the idea of 3 different people seeing and describing the same entity and having witnessed the same ghost while apart from one another demonstrates some of the best proof of ghosts that we know: separate eye-witness accounts with the same description of the paranormal.