Yes i believe in ghosts. The human body has its own energy. It is detectable and measurable with our technology. This electrical energy makes us breath, makes our heart beat, and more importantly is what our brain uses as a 'vessel' for our essence, our personality and thoughts. This point can't be denied as it has been proven.
The first law of thermodynamics is that energy can change forms but it can't be destroyed. again, has been proven.
So if you can't destroy energy, it can only change form, then that means the energy in your body that makes you..well you, will change form when the physical body that contains it dies off.
THAT is a 'ghost'. Residual energy. Thats why you always hear of ghosts that haunt a certain house where they died, or soldiers that haunt battlegrounds where they met their end. The physical form required to create more memories (senses and the physical brain) is not there, the 'energy' can only 'replay' what it 'knows'. You probably dont remember everything in your life, but you would remember your death...right? Thats what a ghost 'remembers'..its death, or some high point that happened in its life. If that person wasn't ready to die, or doesnt know they are dead, those are the ghosts you see that are more than just a 'blob' floating
through the air. Their energy is stronger, less dissipated. They are more tangible. Those are the ghosts that are able to slam doors, make noises..etc.
I think this also explains things like children that are born after a parent dies, but before they actually meet, but have certain idiosyncracies (sp?) that their parents. A child that says something his dead father did, acts a certain way..etc.
atleast thats my .02