MORE LOST BOOKS: As I promised a while ago, I am listing below some additional ancient lost Old Testament pseudepigrapha that I have run across in various places. Some are books that are completely lost apart from their title and perhaps a brief comment on their contents; others are books that are no longer extant, but fragments, quotations, or summaries of them do survive.

A number are listed in the Coptic Nag Hammadi treatise On the Origin of the World (NHC ii, 5 and XIII, 2; fourth century CE or earlier). Some small indication of contents is usually given. It is possible that these are just names made up for effect, but they may well have been real books.

• The Archangelic (Book) of the Prophet Moses (NHC II, 102.8-9)
  
• The First Book of Noraia (NHC, II 102.10, 24-25)
  
• The First Account of Oraia (NHC, II 102. 24-25 -- same book as above?)
  
• The Book of Solomon (NHC II 107.3)
  
• The Configurations of the Fate of Heaven That Is Beneath the Twelve (NHC II 107.16-17)
  
• The Seventh Universe of the Prophet Hieralias (NHC II, 112.23-24)

Hippolytus, in The Refutation of All Heresies (second-third centuries CE), mentions the following:

• The Paraphrase of Seth (5.18.1) (Contains "Sethian doctrines," but evidently is not the same work as the Nag Hammadi Paraphrase of Shem.)
  
• The Book of Baruch (5.20-22; 10.11) (Baruch is the angel of the tree of life, not Jeremiah's scribe in the Bible. This retelling of the biblical narrative by Justin the Gnostic starts with the cosmogony and moves through the Old Testament period up to Jesus. Summarized by Hippolytus.)

Others:

• Quotation of a "scripture" or "prophetic word" with OT content in 1 Clement 23:3-4 and 2 Clement 11:2-4.
  
• A very fragmentary Oxyrhynchus manuscript that seems to involve a vision of heaven and which mentions the Law and the Red Sea. Oxyrhynchus Papyri 17.6-8 (#2069).
  
• A summary of a passage supposedly from a Hebrew noncanonical book pertaining to the prophet Zechariah and King Joash. Found in the fifth-century Historia Ecclesiastica (9.17) of Salaminius Hermias Sozomenus (PG 67.1269b).
  
• "The Rich Man and the Precious Stone," a story told by Georgius Monachus Hamartolos (9th century) in Chron 4.11 (PG 121.228). The passage is supposedly quoted from a book called the Wisdom of Solomon. The quotation was made after 600, so it is perhaps too late for the MOTP Project (but not for its comprehesive list of OT pseudepigrapha).

These were located through the Accordance Software list of Greek Old Testament Pseudepigrapha.

And more:

• Cyprian (some manuscripts only) quotes an otherwise unknown passage "in Baruch" (presumably the scribe this time) in Testimonia 3.29 (third century CE).
  
• An apocalyptic fragment attributed to "the prophet" by Clement of Alexandria (late second-early third century CE) in Protrepticus (Exhoration to the Heathen) 8, end.
  
• A fragment about the Antichrist attributed to "another prophet" (besides Jeremiah) by Hippolytus in On Christ and Antichrist 15

Noted by M. R. James in The Lost Apocrypha of the Old Testament, pp. 77-78, 90, and 92, respectively.

UPDATE (2 September): Ken Penner e-mails some additional information:

You might mention in your blog entry that Denis includes several of the texts you mentioned, in his Introduction, in his Fragmenta, and in his Concordance, e.g., the fragment from 1 Clement 23:3-4 and 2 Clement 11:2-4, the Zechariah fragment, the Fable of the Precious Stone, the fragment from Clement of Alexandria, and the fragment on the Antichrist.

P. Oxy. 2069 is now known to be from 1Enoch.

The Antichrist fragment is also in de Antichristo 54.

The Clement of Alexandria reference in Protrepticus is 10, 98, 1, not 8.

Georgius Cedrenus also has the Fable of the Precious Stone (after the story of Tobit, before king Hezekiah); see I. Bekker, Georgius Cedrenus Ioannis Scylitzae (2 vols.; Corpus scriptorum historiae Byzantinae; Bonn: Weber), 1:193-194.