I think you could make a pretty solid case from the Bible that the spirits of men, once dead, stay dead to this world and are are only active* in another place. In fact, no mainline traditions I know of teach specifically in the existence of ghosts, and quite a few teach against such a thing being possible. There are of course a few exceptional groups claiming to be Christian that have other doctrines, but they are on the fringe and many could arguably be counted as cults.
What is taught and believed by wide swaths of Christianity is that evil spirits are real and can manifest themselves in physical fashions in this world. The exact teachings on this are very diverse, some peddling such an obsession with the spirit world that every shadow comes to hold it's own set of wraiths. Others seem proclaim that the spirit world is irrelevant in our modern times and couldn't care less.
I believe the truth lies somewhere between those two extremes. Most of Protestantism (certainly the Reformed and more conservative circles on down the lines to some pretty generic Evangelical branches) would argue that while evil spirits are real and can and sometimes do have physical manifestations, the important thing to remember is that "He that is in us is stronger than he that is in the world." In other words, as believers in Christ with his Spirit living in us, we have naught to fear from any spirit. Those that are not in Christ run a risk both in not heeding the spirit world and in listening to it and catering to it without possessing any power that can overcome it. I would say the greater risk they run is in their relationship with God not being set to rights, spirits --however real-- should be the least of their worries.
* The timing of this is widely disputed, but is of no consequence to answering this question. Whether spirits sleep until the final judgement or whether the saints are taken directly to be with the Lord doesn't matter here as there is general agreement that this world is no longer their domain.
