There is a pretty good guide over at d3db here .
It includes a spawn point strategy for farming the Act I ghosts.
The diablowiki also has a concise listing here .
Lucious
the Depraved - a unique Grave Robber - found in Cemetery of the Forsaken - Act 1 Dataminer - a unique Ghastly Gravedigger - found in the Defiled Crypt - Act 1 Drury Brown - a unique Ghostly Murderer - found in the Defiled Crypt - Act 1 John Gorham Coffin - a unique Grave Robber - found in the Defiled Crypt - Act 1 Fecklar's Ghost or see also here
- Unique Enraged Phantom-
Festering woods - Act 1
The Archivist - Unique Grim Wraith - The Unknown Depths - Act II
The Tomekeeper - Unique Grim Wraith-
Realm of Shadow - Act II
gaming.stackexchange.com/users/21619/EBongo
The Tomekeeper can be found at the Realm of Shadow in Zoltun Kulle's Archives.
The Dataminer can be found only in the FAKE Defiled Crypt with the Jar of Souls.
John Gorham Coffin can be found only in the REAL Defined Crypt lvl 1(just where the door to the Chancelor's Tomb leads).
gaming.stackexchange.com/users/31610/Tanno
Lucious the Depraved - Cemetery of the forsaken Dataminer - Defiled Crypt Drury Brown - Defiled Crypt John Gorham Coffin - Defiled Crypt Fecklar's Ghost - Festering woods
The Archist -
The Unknown Depths
The Tomekeeper - Realm of shadow Note:
These are random and rare spawns so it wont be easy to find them,also keep in mind to check dead ends.
gaming.stackexchange.com/users/9888/Mentales
I just found The Archivist in The Unknown Depths and he is indeed a Grim Wraith.
gaming.stackexchange.com/users/26526/Riil
Found The Archivist in the Unknown Depths.
Took about 15 runs through, but I found him in a dead end that was no where near the exit.
Good luck.
gaming.stackexchange.com/users/28756/Brian
The Haunted achievements wants you to   Meet the following ghosts:   Lucious the Depraved  Dataminer  Drury Brown  John Gorham Coffin  Fecklar's Ghost  The Archivist  The Tomekeeper    Where are these ghosts located?
Where are all the ghosts for Haunted?
gaming.stackexchange.com
<diablo-3>
gaming.stackexchange.com/questions/67965
gaming.stackexchange.com/users/7816/Ian Pugsley
the Depraved is found in Cemetery of the Forsaken,  - Dataminer  is found in the Defiled Crypt, Drury Brown is found in the Defiled Crypt, John Gorham Coffin is found in the Defiled Crypt, Tombkeeper is in the Realm of the Shadow. While random spawns, the ghosts for haunted are commonly appearing in specific locations.
The community lists areas, regarding the locations of ghosts for haunted.