LOST BOOKS MENTIONED IN THE BIBLE are noted by Daniel Hopkinson, the "Knoxville Evangelical Examiner" for The Examiner:

The other books mentioned within the Bible pages:
August 3, 5:07 AM

The very King James Bible (among other translations as well) that so many insist is complete and having no need of other books to be included in it, mentions several other books over the course of the 66 books contained in the official canon that at one time were evidently prominent in that particular author’s thought that mentioned it, a few of which may actually refer to books already included in the canon.

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Mr. Hopkinson has been writing a lot lately about apocrypha and pseudepigrapha -- apparently unaware of even the most basic and foundational secondary literature (e.g., the Charlesworth edition of the Old Testament Pseudepigrapha), so I haven't been noting his articles. But this one interests me particularly, since I've done a lot of research on these lost books and am publishing a translation of their surviving fragments for the More Old Testament Pseudepigrapha Project ("Quotations from Lost Books in the Hebrew Bible").

His list is fairly complete, but leaves out some things, such as the other two quotations in Numbers 21:16-18, 21-25; another possible quote from the Book of Jashar in the LXX of 1 Kings 8:53 (cf. 1 Kings 8:12-13 MT); a book by Samuel on the conduct of kingship in 1 Samuel 10:25; the Book of the Acts of Solomon in 1 Kings 11:41; the Book of the Chronicles of King David in 1 Chronicles 27:23-24; King David's plan from YHWH for the Temple in 1 Chronicles 28:19; and the Laments (over King Josiah) attributed to the prophet Jeremiah in 2 Chronicles 35:25. It is likely on various contextual grounds that the apparent prophetic books quoted in 1-2 Chronicles are actually references to passages in the Chronicles of the lost Book of the Kings of Israel and Judah, which in turn is likely a digest of the lost Book of the Chronicles of the Kings of Israel and the Book of the Chronicles of the Kings of Judah cited in 1-2 Kings. It is interesting also that Ezra 6:18 attributes material to "Moses" which is not found in our Pentateuch.

There are also other references to lost OT pseudepigrapha in the New Testament: the Testament of Moses in Jude 9, and perhaps the Apocalypse or Apocryphon of Elijah in 1 Corinthians 2:9 and the book of Eldad and Modad in James 4:5. Richard Bauckham will be providing contributions dealing with all three of these in MOTP. The quote in Ephesians 5:14 may also be of a lost apocryphon. (There are other NT quotes of OT pseudepigrapha that are not lost, or not entirely so: 2 Timothy 3:8 refers to Jannes and Jambres and Jude 14-15 quotes from the Book of Watchers [1 Enoch 1:9]).

For more on all of this, see the relevant MOTP chapters, which should be going to press soon.

I am not a specialist in the Pauline letters or the NT Apocrypha, but those who are agree unanimously that the Epistle to the Laodecians is a forgery from well after Paul's time. As Mr. Hopkinson says, you can make up your mind for yourself.

For more on lost books, see here and follow the links.