Nice topic for Halloween. This weeks episode of Paranormal State they needed to do a exorcism on a girl. Paranormal State is not my favorite ghost show, but I thought this one was really interesting. I would say that watching this is a lot more scarier then watching the movie the Exorcist.
Here is the Youtube link to the first of 6 parts. I would probably skip the first two parts, from 3-6 is where the excitement is. I would have just embedded them, but the idiot that posted the videos disallowed embedding.
So instead here are some other exorcism videos if you are too lazy to click on the link.