Generally, I'm not a believer. Some strange things have happened over the years, but I don't believe in ghosts.
I do have some stories, but I am very skeptical.
1. My girlfriend's friend was staying at the "jail hostel" in Ottawa and claimed she saw a ghost. She doesn't know much English, but sounded terrified when she talked to my girlfriend in Japanese. She was obviously very shaken for the next few weeks.
2. My sister claimed she saw a ghost in the corridors of Edinburgh castle. She was 7 at the time. I should ask her about this now as she's going to be 27 next month. Maybe she could shed some light on it.
3. The only instance that involved me. My family and I were on holiday in Gran Canaria. I was five. We checked into our hotel (which was actually a seperate reception building, then a series of Villas). The room I was staying in had a window facing reception. During the night, I couldn't sleep as I could hear the faint sound of what sounded like a female choir. Not singing anything in particular. More like humming with vibrato. It sounded so distant and haunting. I could see the light was still on at the reception. The noise stopped and I was able to drift off to sleep. A little while later, I woke up and saw the reception light was still on. I tried to get back to sleep and before I could get to sleep, the light at the reception went off. This was easily 3 or 4 am.
I asked my dad about it the next day and he said it must have been the wind. As for the reception, it wasn't a 24 hour reception and generally closed early the rest of the time we were there. I am aware of the possibility that some of the staff lived in the reception building, so that may explain why the lights were on so late that one night. However, it creeped me out.
I never heard the noise again.
EDIT:
Wow Baly, that's quite a scary story.
EDIT2:
Good choice of advertising for this thread.