Is there a specific term for the labels used in offices and other places, which are mounted outside a person's office or cubicle and carry his name and other details?
As an alternative to "nameplate", the term plaque /plak/ refers to an object affixed to a wall, door, or other surface that has an inscription or decoration on it. It is often used to identify or commemorate somebody or something.
A door plaque would be affixed to an office door and might have the name and title of the person who occupies the office. It might also identify the room. (For example "Conference Room A" or "Engineering Dept".)
A wall plaque, mounted to a wall near the door, can serve the same purpose.
Q. Are you the head of security? A. That's what the plaque on the door says.
While toblerones has been mentioned (cited in comments without references) as meaning nameplates around a conference table, the term place card or possibly name card is more likely to be used in that context. A place card is “A card set down at a table to inform a guest where they are to sit”.
Nameplate has already been mentioned. A nameplate is “A plate or plaque inscribed with a person's name, especially one on an office door”.
An alternative to nameplate as an office label is doorplate, “A plaque mounted on a door bearing information about the occupant or a room or building”.
Two more terms occasionally (but rarely) used for this purpose are:
• escutcheon, of which OED1 says “3. Anything shaped like, or resembling, an escutcheon: ... c. A key-hole plate, a name plate, etc.”
• placard, “A sheet of paper or cardboard with a written or printed announcement on one side for display in a public place”.