The primary distinction between spirits and ghosts as understood by other researchers, is that ghosts are earthbound, whereas spirits have allegedly passed on to the light and are free to move between realms. Both types are known as discarnates. 

Phantoms - These are ghosts which so closely resemble the living that they are often not realized as ghosts until they do something uncanny, like walk through a wall. 

1) Phantom Hitchhikers - According to many urban legends, these are ghosts who typically interact with the living in such a way that they ask for a ride, and before arriving at the destination, they mysteriously disappear. Usually occurs on the anniversary of their death.  

2) Phantom Travelers - Ghosts that are found along a certain route, usually as a result of a deadly accident . They can be riding horses, or prepared to board a train or plane. Most manifest on the anniversary of their death

Apparitions - Ghosts which are clearly such are known as apparitions. There are several different categories:

1)  Atmospheric  - Also known as a residual or replay haunting, these are typically seen in only one location repeating a certain action again and again, usually something attached to a traumatic event. I discuss this more under Location Based.

2)  Crisis or Deathbed - These appear to family or friends around the time of death. According to Trent Brandon: "They are very common ghost sightings, but almost never occur more than four days after death."

3)  Family - Ghosts which are connected to a particular familiy, they often foretell death and disaster. 

4)  Haunted Objects - Instead of haunting a location, a particular object is the anchor for a ghost. 

5)  Object Apparitions - Manifestations of ghostly items which can be natural or manmade objects. 

6)  Photographic - Ghosts that are not seen until after a photo is taken and examined. These MAY include orbs, mists, (ectoplasm) vortexes, shadows and other unusual light or optical effects. Many debate whether they are actually ghosts, spirits, or souls; personally I feel they are some kind of energetic or spiritual byproduct.  

7)  Historical - These are like atmospheric except they have can be seen in more than one location going about their business. Non-interactive, so they would fall into Location Based. Typically dressed in period clothing and often appear solid. 

8)  Recurring - Ghosts that appear on a certain time schedule or anniversary; usually annually.

9)  Modern - As Historical, but they resemble more contemporary people.

10) Transportation - Also known as Phantom Craft under Location Based, they are often associated with the final moments of some tragic accident. The wreckage itself can attach energy in such a way as to become haunted. There are some kinds that are not necessarily relegated to one location, but can be seen anywhere that it would have normally been seen in pre-spirit existence. The Flying Dutchman is a famous example and is usually sighting one is a bad omen.

11) Marian - What some believe to be appearances of the Virgin Mary. This could also cover cameos by other saints or religious/spiritual figures.

12) Out of Body - The appearance of a living person who is actually in another location. They are not necessarily ill or dying, and can be either solid or translucent. Some claim to recall their OBE and can give verifiable details about the location they were seen. Probably related to Astral Projection.

13) Battlefield - Also known as floating battlefields, they resemble an actual reenactment of war, but for some reason, they typically occur above the ground. From several to a hundred feet up, in some cases.

14) Grey Ladies - The ghosts of women who died in sadness over love or betrayal. Can be white, grey or black.

Classic Haunting - Also known as a Entity Haunting, it is defined as an interactive ghost which does not fall into any special category such as those mentioned above. Can be a phantom, apparition, presence, or unexplained events which occur in a certain location.

Graveyard Spectres - Also known as shells or shades, these are believed to be the etheric remnants of a person after death. Commonly found in graveyards days or weeks after a burial, they are scary but not dangerous. Typically seen as dark, shadowy forms they usually do not communicate or talk. Legend has it that people were buried alive in new graveyards to create a guardian, known as an ankou. 

Etheric Revenant - A very rare, but dangerous undead creature that feeds upon energy from the living, it is the original vampire of legend. This is detailed more in John Greer's book "Monsters" described on my books to read page.