Personally, I have had two separate experiences with ghosts. The second one happened three years ago. Our high school's auditorium is famous for being haunted, and all sorts of crazy things happen all the time. One of the most prominent ones is that, when you're up on the lighting deck(the balcony off-stage-right that controls all the lights in the auditorium and on the stage), you'll start to hear the sound of a heavy door closing over and over. It comes from somewhere in the wall, and has never been explained. The balcony isn't level with either the first or second floor, it's in between the two. Now, due to some acoustical phenomenon, the door could be somewhere on either floor and still sound like it's coming from right next to the wall.... but there's no heavy door anywhere in the school that closes that often(my sister is now in 10th Grade drama and had the oppourtunity to time it last week.... 26 times in less than 10 minutes).
On top of this, after noticing it for a while back when we were in 10th Grade, my friend and our drama teacher about it. He says it's been happening as long as he can remember. It even happens when they're rehearsing at night when nobody else is in the school.
It's
extremely frightening when you're up there doing the lights for a skit, by yourself, and it's pitch black, as I have been on two or three occasions.
Now, as for the actual experience there, my friend and I spent a period that year taking pictures with his digital camera. What we were actually trying to get was photos of
orbs, just to see if we could because people had there before.
We had been unsuccessful so far. We'd take random pictures, as well as a few that involved us asking "the ghost" if we could take it's picture, and if so, to move a piece of string or something hanging from various places. If the string starting to move, we'd photograph it. Still, nothing unsusal there.
Then I took one of the whole auditorium, from the stage, and there, in the center of the photo against a far wall, was a small white object. Here's my jpeg of the photo.
Now this may not look like much, but on his camera, in high resolution, we zoomed in and, in all seriousness, it looked so much like a face that since then, I've honestly been able to say that yes, I do believe in ghosts, whatever they may really be. I figure that's as close to reasonable proof as I can get short of actually seeing a ghost*, a photo I took myself.
Oh, and the next photo we took was loaded with orbs. Go figure.
*Funnily enough... I may have seen one about 5 years earlier at a Karate tournament in a church. About eight of us were going down a hallway to look in the "haunted room" where a sunday school teacher had been strangled, or so the story goes. The door appeared to have opened by itself so we were walking down the hall and, as I remember it, she looked like the to half of a woman made of steam and cobwebs. We ran.
Since posting this I've met one of the kids who was in this group and asked him what he remembered seeing that day. Same thing, down to the details.