From the Supplements page @ Supplements it appears that the following are the most-recent/last known printings of the OD&D Supplements by TSR:

- Greyhawk = 12th
- Blackmoor = 9th
- Eldritch Wizardry = 9th
- Gods, Demigods, & Heroes = 7th
- Swords & Spells = 6th

There's also this note:

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.

Other than the "official" photocopies mentioned above, are there known printings that are later than the 1979 printings?  The books themselves were still for sale through the Dungeon Hobby Shop catalog through 1986, at least, but those may have been the remaining stock of the Nov 1979 printing, too.