In the Bible, I Kings 4:32, it says that King Solomon wrote 3,000
proverbs.  I know that a good percentage are in the book of Proverbs. 
Where are the rest?  Thank you.

This may be of interest to you:

"Works attributed to Solomon have existed in different ages, from his
time till the present. Eusebius states that Hezekiah, finding the Jews
putting too much confidence in the books of Solomon, relative to cures
and different occult arts, ordered them to be suppressed. Josephus
positively says that Solomon did compose books of charms to cure
diseases, and conjurations to expel demons, Antiq., lib. viii., cap.
2. He states farther, that a Jew named Eliezar cured several demoniacs
in the presence of Vespasian, by reciting the charms which had been
invented by Solomon. R. D. Kimchi speaks of a book of Solomon entitled
The Cure of Diseases, which Genebrard supposes to be the same work of
which Josephus speaks. And Origen speaks of conjurations which were
used by the Jews in his time, and which they professed to derive from
the books of Solomon. There are still extant books of this kind
attributed to Solomon, such as The Enchantments, The Clavicle, The
Ring, The Hygromantia, The New Moons, and The Shadows of Ideas; but
these, as they now stand, are the inventions of quacks and impostors,
and entitled to no regard. If there were any books containing the
wisdom of Solomon, they are either irrecoverably lost, or exist in
mutilated fragments among the Asiatic sages; and are disfigured by
being connected with improbable tales, and pretended mantras or
charms."

http://www.godrules.net/library/clarke/clarke1kin11.htm

TO GIVE A PROPER ANSWER TO THIS INTERESTING QUESTION, IT IS NECESSARY
TO UNDERSTAND THAT THE WHOLE BIBLE IS INSPIRED OF GOD. EVERY ONE OF
THE FORTY WRITERS OF THE VARIOUS BOOKS IN THE BIBLE WERE INSPIRED TO
WRITE WHAT THEY DID. IF YOU STUDY THE WHOLE BIBLE FROM GENESIS TO
REVELATION, YOU WILL DISCOVER ITS THEME.. THE COMING OF GOD`S
"KINGDOM", THE SAME KINGDOM THAT JESUS MENTIONS IN THE "LORDS PRAYER"
AT MATTHEW 6; 9,10. THE BOOK OF PROVERBS IS ONLY A SMALL SELECTION
THAT SOLOMON KNEW. THESE ARE GIVEN AS A SAMPLE OF SOLOMONS WISDOM. IN
1 KINGS 3;5, THE BIBLE STATES THAT JEHOVAH GOD APPEARED TO SOLOMON AND
SAID " REQUEST WHAT I SHOULD GIVE YOU". VERSES 6 TO 9 SAY THAT SOLOMON
REQUESTED KNOWLEDGE AND WISDOM. JEHOVAH GOD GRANTED HIM THESE AND ALSO
AS STATED AT VBERSE 13, JEHOVAH GOD GAVE HIM RICHES AND GLORY,AND A
LONG LIFE,  SIMPLY BECAUSE SOLOMON HAD NOT ASKED FOR THESE. IF YOU
WONDER WHERE THE NAME JEHOVAH COMES FROM, LOOK UP PSALM 83;18. IF YOU
FINF IT HAS BEEN SUBSTITUTED WITH THE TITLE "LORD", THE FRONT PAGE OF
YOUR BIBLE WILL EXPLAIN THE TETRAGRAMMATON. HEBREW Y.H.W.H. OR
YAHWEH... GOD`S PERSONAL NAME... LORD IS HIS TITLE. THE WHOLE BIBLE IS
A GUIDE TO A GOOD LIFE WHERE JEHOVAH GOD COMES FIRST.. ECCLESIASTES
12;13 SAYS...THE CONCLUSION OF THE MATTER, EVERYTHING HAVING BEEN
HEARD IS, FEAR THE TRUE GOD AND KEEP HIS COMMANDMENTS, FOR THIS IS THE
WHOLE OBLIGATION OF MAN.