Dust Jacket (photo available), four impressions with slight differences, Illustrated by J.R.R. Tolkien.  It's best to know exactly what you're doing before buying a first editon.  Market values are based on impression, condition and completeness, and prices can vary by thousands of dollars.  Detailed descriptions of first and second states can be found in Hammond and Anderson's descriptive bibliography.

Dust Jacket, cloth boards, blue titles, map end papers.  Illustrated by J.R.R. Tolkien.  Early copies were printed in Great Britain.  No printing date or number indicated until the 18th printing, and though the text was updated, impression numbers did not revert to one, so second editions are actually printings five through 23 - as Houghton Mifflin counts it.  It is possible that the actual number was 21.  Are we surprised?  No, we are not.  These are also hard to identify and have significant collector value (in an original jacket) - research before buying.

Dust Jacket, Green cloth boards, blue titles.  Illustrated by J.R.R. Tolkien.  Neither edition nor print year was stated.  Brand new shiny USA copyright 1966 clearly stated.  They were given the ISBN 0395071224 after 1969.  With Tolkien's popularity rising, these were printed in greater numbers, and are quite a bit more affordable - though you still won't find many in nice jackets.

Dust Jacket, Green or blue cloth boards, blue titles.  Illustrated by J.R.R. Tolkien.  The date given here is the earliest US copyright record for this ISBN, which now claims to be "consistent with" the George Allen & Unwin (UK) 1978 4th edition.  The publishing date is not stated inside, but indicated in the numbers on the lower left of the dust jacket front flap.  Because HMCo and US recording data and UK operations were all out of synch, it often happens that the edition date, printing date, and copyright date are three different dates... which is why I list by ISBN.  Final RRP $16.99

Harry N. Abrams, Film by Rankin & Bass, Dust Jacket, Illustrated by Lester Abrams.  The jacket is clear acetate with Smaug printed on it front and back, so without the jacket (which is easily damaged), the cover art is incomplete.  RRP $29.95

Dust Jacket, glossy paper over boards, illustrated by Michael Hague, 40+ color plates.  RRP $19.95 - $29.95

Dust Jacket, green cloth, gilt titles, 5 color plates, illustrated by J.R.R. Tolkien.  A search for this ISBN does not turn up any of these, and while I would swear that they exist, it seems that they were not mass marketed.  The ISBN is valid, and was apparently assigned to The Hobbit.  Perhaps HMCo decided to publish only The gold 50th anniversary slipcased collector's edition (9780395177112), which is often mistakenly (or intentionally) listed under this ISBN.  RRP $29.95
 

Slightly oversize, cloth over boards, Dust Jacket, annotated by Douglas A. Anderson.  Illustrated by J.R.R. Tolkien and including many more images in the notations, which are in the margins.  Contains the complete text and illustrations, and I found this very fun - but if you just want to read the story, the notes may be a bit distracting.    RRP $9.99

Galahad Books, art from the film by Rankin & Bass
There is a printed paper dust jacket for this reprint, and I believe the pictoral cover has the same art - I've never actually seen one in person... or maybe I just wasn't paying attention...  RRP $15.99

Random House Value Publishing.  Dust Jacket, Notes by Douglas A. Anderson.  RRP  $9.99
 

Green cloth, gold gilt dragon design on the front cover, Dust Jacket, Illustrated by Alan Lee with 25 color paintings and 38 black-and-white drawings.  Printings not stated.  Still available new.  RRP $35.00
 

Black quarter cloth, dust jacket illustrated by Peter Sis.  This is the first editon to claim, after 64 years of printings, to have fully corrected text, and is considered to be the 5th US edition. 
RRP $18.00
 

Black paper over boards, exclusive dust jacket illustrated by Donato Giancola, contains the fully corrected text, available new to club members from SFBC.  RRP $14.99 plus shipping and handling.  UPDATE: Base RRP reduced to $10.99 - $12.99 depending on which of the Doubleday book clubs purchased from.
 

Houghton Mifflin.  Notes by Douglas A. Anderson.  Dark green paper over boards, dust jacket, reinforced spine, still available new.  RRP  $30.00 - $35.00

Dust Jacket, green cloth, gilt titles, 5 color plates by Tolkien.  Nothing much new except put together exactly as Tolkien originally wanted it, red sun on the jacket and all.  And, we're playing silly buggers again... this now identifies all over the internet as the 75th Anniversary Edition.  It is the exact same book and still identifies as a 70th Anniversary Edition on the copyright page.  The only difference is a round, gold, 75th Anniversary sticker on the dust jacket, which started appearing by the 11th printing.  Available new, RRP $25 - $26
 

Small hardcover with dust jacket, 4.25 x .85 x 5.88 inches.  Green cloth, gilt titles, black and white illustrations.  RRP  $15.95 - $16.99
 

Hardcover, rather lovely decorated green cloth over boards, fully illustrated by Jemima Catlin.  The copyright info is nuts.  The title page gives Houghton Mifflin as the publisher, the copyright says First US Edition, Published by Harper Collins.  The first printing was printed in China, later Slovenia, later just "Europe".  I begin to think my work here is coming to an end.
Available new.  RRP  $35