This is quite a hard area to catalogue as there are a large number of ad-hoc cards produced. This list is nowhere near complete and mainly focuses on the mainstream 'officially' produced items.
The definition of a Postcard is a bit subjective, mine is a single printed card with picture on the front with blank message and postage details on the back (sometimes Greetings cards are are also Postcards, but come with envelopes, I am not including those here).
There are also a lot of printed picture cards which are often promoted as postcards, which I haven't included.
There are also a lot of 'unofficial' postcards from Asia, also not included.
Books
These contain pull out individual postcards within them.
Tolkien
Tolkien's Middle Earth
The Lord of the Rings
Tolkien's Hobbit
Tolkien's Middle-Earth & Monsters
Tolkien's Dragons & Monsters
The Bothers Hilderbrant Their Tolkien Art
Magnetic Postcards Book
0762409533
JRR Tolkien: Bilder aus Mittelerde
German
The Tolken Artwork of Greg & Tim Hildebrandt
Calendar with Postcards
WETA
Lord of the Rings
Hobbit
Sets
Bodleian Library Manuscript Set
Bodleian Library Tolkien Drawings
Bodleian
Bodleian Library Middle Earth Exhibition
Tolkien Art Set
Come with the Hobbit 75th annversery pocket edition.
Tolkien Art Set
Comes with the Hobbit facsimile book
Tolkien Portraits Set (Pamela Chandler)
Robert Rosenthal Hobbit
1979
Renshof and Ploeg (Artist)
Limited 250
Signed
Jimmy Cauty (Artist)
Peter Pracownik (Artist)
Bakshi DVD set
Free with limited edition DVD package
Artists
Lord of the Rings Musical
Exhibition
Tolkien Society
Anke Eissmann (Artist)
13 cards in each set
Set 1
Set 2
Set 3
Map series
Movie Fan Club Exclusives
Fellowship movie
Two Towers set
Trilogy
Japanese
Classico Sets
CL8-014
CL8-015
Air New Zealand
Hobbiton Film Set New Zealand
Hobbiton Film Set New Zealand
www.lordoftherings.net
Lord of the Rings Movies
Posters
Pyramid
Unexpected Journey movie
Decipher TCG Promo
Stamps
These are postcards featuring stamps
New Zealand
Fellowship
Isle of Man
Return of the King
Singles
Hans Arnold
1978
Hobbiton USA
Tolkien Flower and Rock Garden
1970s
Puffin Hobbit (Pauline Baynes)
Pauline Baynes
Bilbo's Last Song
Barnes and Noble
Film tie-in book promotions
Fellowship Movie DVD Promo
Movie Network Cinema
Stand ups
Cineworld
EA Games
Third Age Game, Return of the King Game
Third Age Game
German
Rough Guide Book Promotion
National Reading Campaign
Boomerang PC