According to Webster's Dictionary, a wraith is the apparition of an individual before or slightly after their death. It is not necessarily a ghost, as ghosts are related to longer-term apparitions. This page is devoted entirely to the wraith, both the traditional meanings as well as more modern interpretations. Links provided will take you to pages and books containing sometimes useful, sometimes free, and always interesting information regarding this topic.
Erring on the Side of Folklore:
Loosely related to Ghosts, as described in Wikipedia. (Under "English Terminology": Scottish wraith of obscure origin). For more specific descriptions Monstropedia also has some interesting information gleaned from the Wikipedia article. You'll still need the Wikipedia page to find the references, however.
Publications of the Folk-Lore Society, Volume 35: Under "Warnings" page 266. This volume approaches the literal interpretation of a wraith with case studies and corroborated stories, as well as the author's own experiences.
British Folk Tales and Legends: Another book snippet (Part 16, page 309) this time focusing on wraiths in stories and legend. It's a bit short, however.
Folk Lore: (page 64) This is especially interesting as it takes on the "rules" regarding when and how one can see a wraith, what these factors mean for a sighting, and where these sightings can take place (rules varying with location), as well as further legends.
Catholic World, Volume 85: (page 3) Despite the title, the section pertaining to wraiths spends more time promoting telepathy than religion. This is probably the most interesting with regard to the stories presented. Unfortunately, the section ends with a cliffhanger, and I haven't yet found the continuation. (It's not a story, but a clever article.)
The Wraith of Garry Water: (page 110) Old Irish poem by Charles Mackay featuring an ominous girl and a reprehensible guy. Probably more closely related to the concept of a "water wraith" but a fun poem nonetheless. Interesting in that it promotes the notion that animals are better at sensing the supernatural than we humans ever could.
County Folk Lore, Volume 2: This book was written by the Folklore Society in Great Britain. The Wraith section is short (about a page) and falls under the heading of "Goblindom." It does, however, breach the subject of the Doppelganger as an omen of death, as well as how to survive this encounter. In here, a wraith is seen as a kind of doppelganger, which really isn't much of a surprise, as a doppelganger is a double of an individual.
Doppelganger: The ghostly counterpart of a person. (Merriam-Webster)
Doppelgangers in Fiction: Everything doppelganger. (...I just really like that word.) This one really goes in depth with the concept of doppelganger.
Modern Perspectives: This is how we view wraiths today...
Although there is a kind of inkling telling us what a wraith might be, modern interpretations have worn down the meaning to the point where pretty much any ghostly or supernatural creature can be called a wraith. The list extends from drag racers to comic heroes to music albums, and goes on and on....
Charlie Sheen's 1986 movie. I'm not really sure what language that is, but the movie is in English.
The Car is the important part, though...(to me, at least.) That is a lovely car...check out those Lambo doors!
This is actually an album (two albums, The Wraith: Shangri-La and The Wraith: Hell's Pit) by the Insane Clown Posse. Very creepy, yet often very fun music in the "horrorcore" genre.
The Wraith Comic...because EVERYTHING MUST HAVE A COMIC!!!!
Stargate Loves Wraiths! Sci-Fi, back when it was still spelled right. We're almost completely divorced of the original meaning at this point...let us head back.
Recent interpretations brought on by literature and the movie industry take us back towards the wraith's dictionary definition, though not without some added spice.
Dementors from Harry Potter take us a bit closer to the original...especially since their presence spells doom for pretty much everybody.
The closest: Ringwraiths from The Lord of the Rings. This is because they are confirmed wraiths of deceased individuals, minus the cool cars and albums and species divergence presented by the others. They do, however, get matching horses and Nazgul...but fantasy is allowed to play with folklore like that.
That is all for now. A little bit of everything--I'll add more when I discover more.