Greyhawk:  Supplement I by Gary Gygax and Rob Kuntz
Blackmoor:  Supplement II by Dave Arneson
Eldritch Wizardry:  Supplement III by Gary Gygax and Brian Blume
Gods, Demi-Gods, & Heroes:  Supplement IV by Rob Kuntz and James Ward
Swords & Spells by Gary Gygax

Greyhawk is a general rules expansion, with new combat rules, additional character classes (paladin and thief), as well as new monsters, spells, and treasure.

Blackmoor is the second expansion, adding underwater rules, two new character classes (monk and assassin), and hit location rules.  It also contains the first scenario ever published for a role-playing game, "Temple of the Frog", which was later developed into module DA2 Temple of the Frog.

Eldritch Wizardry adds the druid character class, additional magic items and artifacts, as well as rules for demons and psionics.

Gods, Demi-Gods, & Heroes supplies pantheons of deities, including their monster-style statistics  (unfortunately giving players the idea that gods are killable).  It includes the Melnibonean mythos, which (along with the Cthulhu mythos, not present in this booklet) created legal problems for its successor, the AD&D manual Deities & Demigods.  However, that book bears only a passing resemblance to this supplement's contents.

Swords & Spells is the fantasy-based successor to Chainmail, covering miniatures rules for D&D.  It was hastily produced, and contains several glaring errors.  While it was the fifth (and last) supplement for OD&D, it was never labeled as such.

Printing Information

Greyhawk:

• The First printing of Greyhawk (with the "GK" logo), when compared to later prints, shows the following differences: it has the words "Additional" and "Supplement I" in a different, expanded-style font, the cover artwork is slightly larger, and the internal typeface is much more condensed (similar to that of the early Original D&D Set booklets).  Also, the price for a "Multi-Dice Set" in the rear catalog has "$1.75" scratched out, and "$2.50" hand-written in pen next to it.  The booklet is 56 pages long, and was printed by Graphic Printing of Lake Geneva.  The inside cover does not have a printing date, though we believe it was printed in March 1975.  Being released in roughly the same time frame as the Second Print of the Original D&D Set (of which only 2000 copies were printed), it is easy to surmise that the print run of this version was 1000 copies or less.  (Thanks to Bruce Robertson and Jon Peterson for this info).
  

• The Second print of Greyhawk bears either a GK logo or a Lizard logo, with cover text/artwork size differences as depicted in the scan to the right, and is now 68 pages long (due entirely, it appears, to the new internal typeface).  Though both versions state "Second Printing, July 1975" on the copyright page, the Lizard-logo version was actually printed between September and December 1975.  The Second print (and all later printings) were printed by Heritage Models of Dallas, Texas.  (Thanks to Jeremy Simmons for help with this info).
  

• Second prints and later of Greyhawk have multiple textual errors.  These errors were never corrected in the main body of any subsequent print; however, an errata sheet appears on the last page of the Third and later prints. (Thanks to Joss Ellis for this info, and for the scan of the errata page).
  

• Beginning with the Third print, the cover illustration was slightly enlarged over previous prints.  (Thanks to Joss Ellis for this info, and to Adrian Newman for the scan of the Eleventh print).
  

• All prints continue to reference "Hobbits" on page 5, long after the other Tolkien references were corrected  (Thanks to Stewart Brown for this info).

Eldritch Wizardry:

• The First printing has the printing notice on the first page all in lower case ("printed in u.s.a.").  Additionally, the First print does not have the "Tzoonk Fragment" concerning the Codex of the Infinite Planes, on page 43: 

  "...and thereupon the voice belled forth in tones of hollow iron and spoke of the Coming of the City of the Gods.  Such future events interested me not, no I gave the command: 'Answer in th...' (here the fragment becomes entirely illegible)... so knowing both the secret and the spell which would unlock the Way to this horde of the Demon Prince Nql... (another break in the writing unfortunately occurs here)... gathered the nine as required and proceeded forth.  With me in addition were the dyoph servants necessary to transport the Code [sic], for I would not leave it behind on even so perilous a journey as this." (Here the entire fragment ends.)

  The printing notice was correctly capitalized in Second and later prints.  The Second print, like the First, does not have any printing # or date on the first page; most likely, it was printed either in July 1976 or April 1977).  (Thanks to James Bandy, Bryan Manahan, and Michael Falconer for help with this info).
  

• The First print's last page is labelled "Products List"; subsequent prints are labelled "Other Fantasy Releases By TSR" (and have the expected updated product listing).  (Thanks to Alban Jalabert for this info).

• The First through Fourth printings identify the drawing on page 3 as a "Balrog"; this reference is omitted in the Fifth printing and later (due to the Tolkien copyright issue).  (Thanks to Martin Ansell, David Ray, Bruce Robertson, and Terry Sikes for help with this info).

Gods, Demi-Gods, & Heroes:

• The numbering sequence of prints skipped over the Fifth printing, and was only corrected much later.  Therefore, the "true" Fifth printing is labeled "Sixth (11/78)", the "true" Sixth is labeled "Seventh (4/79)", and the "true" Seventh printing is (finally) correctly labeled (11/79).

Booklets in general:

• First printings do not have any printing number on the copyright page (just the year of copyright, such as "Copyright 1975").  Subsequent printings do have the printing number (with the exception of the Second print of Eldritch Wizardry, which does not).
  

• Sep 75:  GK symbol ("Gygax/Kaye") replaced by Lizard logo, and "Tactical Studies Rules" replaced by "Published by TSR Rules". Price ($5.00).
  

• Mar 78:  Price removed from cover.
  

• Dec 78:  Lizard logo replaced by Wizard logo.
  

• Nov 79:  All booklets printed one final time.  Swords & Spells has the "Published by TSR Rules" replaced by "TSR Hobbies" and an address, for the Fifth and later printings.  Note: black-and-white reprints of the Nov 79 editions were also later released, probably as stocks of that print ran out.  They are basically photocopies; some sources have reported paper-thin covers, while others describe covers identical in weight to the normal tan-colored versions.
  

• We don't know which printings may have originally come shrinkwrapped; we know that the last (Nov 79) printings did, but are unsure of any earlier printings (thanks to Rick Bauer for this info).

Aside from the notes above, the only difference between printings is the printing number and date noted on the copyright page (remember that First printings, and the Second print of Eldritch Wizardry, do not have a printing number):

Some astute collectors pay attention to the actual printing #, and will pay markedly higher values for early printings.

Shrinkwrapped condition has only been verified for the last (Nov 79) printings.

• Greyhawk: Supplement I
• Blackmoor: Supplement II
• Eldritch Wizardry: Supplement III
• Gods, Demi-Gods, & Heroes: Supplement IV
• Swords & Spells: Supplement V