Yes I do believe in ghosts, but unfortunately have never seen one.
I have often felt what I suspect was a ghost at times, and I also seem to be sensitive to different energies in a room. This only makes me more disappointed that I haven't ever seen something more definitive.
I did however have someone I know 'appear' in front of me once, for about a minute or so. I thought that she must have died, but found out later that she hadn't.
So I'm not sure what that was all about.
What about you, have you ever seen a ghost? :)