1. The oldest version of the material, from 11QPs\a (=11Q5) is contained at the end of a fragmentary leather scroll in Hebrew (parts of at least 34 columns [28 cols in the largest connected section]) from about the 2nd quarter of the first century CE that includes 51 separate psalms and related items, mostly Psalms 101-151 but sometimes in different sequences-- [frag A,B,C] 101 - 102 - 103 || [frag D] 109 -  || [frag E] 118 - 104 - 147 - [joins col 1] 105 - [col 2] 146 - 148 [+120] - [col 3] 121 - 122 - 123 - [col 4] 124 - 125 - 126 - 127 - [col 5] 128 - 129 - 130 - 131 - [col 6] 132 - [cols 6b-14a] 119 - [cols 14b-16a] 135 - 136 - [col 16] Catena (from Ps 118) - [col 17] 145 [+ Another Psalm? || col 18] - 154 (=Syr #2) + [col 19] Plea for Deliverance - [col 20] 139 - 137 - [col 21] 138 - Psalm in Sirach 51.13-19...30 - [col 22] "Hymn to Zion" - 93 - [col 23] 141 - 133 - 144 - [col 24] 155 (=Syr #3) - [col 25] 142 - 143 - [col 26] 149 - 150 - [col 26.9] "Hymn to the Creator" - [col 27] - "David’s Last Words" (1 Sam 23....7) - "David’s Compositions" - 140 - [col 28] 134 - 151a + 151b - blank col 29 [end of scroll].
 A Hallaleujah of David, son of Jesse
I was smaller than my brothers and the youngest of my father's sons;
And he made me  shepherd of his flock and in charge of his kid goats.
My hands made a flute, andf my fingers a lyre,  and I gave to YHWH glory.
I said in my soul: the mountains do not witness  to me and the the hills do not proclaim for me --
the trees my words, and the flock my deeds.
 Who, then will proclaim and who announce and who recount my deeds?
The Lord (Adon) of all saw, the God  of all, he heard and he listened.
He sent his prophet to anoint me, Samuel,  to make me great.
My brothers went out to meet him, handsome of form, and handsome of appearance.
Though they were tall in stature,  handsome [blank] their hair,
YHWH God did not choose them, but sent to fetch me  from after the flock
and anointed me with holy oil and made me leader of his people /and ruler/ over the sons of  his covenant. [blank]
 Beginning of David's power after the God's prophet had anointed him
Then I saw a Philistine  threatening from [ . . . ]
2. The 11QPsa text (column 27) includes a summary statement about David's psalms and songs numbering more than 4000!
 And David, the son of Jesse, was wise, and a light like the light of the sun, and literate,
 and discerning and perfect in all his ways before God and men.
 And the Lord gave him a discerning and enlightened spirit.
And he wrote 3,600 psalms;  and songs to sing before the altar over the whole-burnt
perpetual offering  every day, for all the days of the year, 364;
 and for the offering of the Sabbaths, 52 songs;
and for the offering of the New  Moons and for all the Solemn Assemblies and for the Day of Atonement, 30 songs.
 And all the songs that he spoke were 446, and songs  for making music over the stricken, 4.
And the total was 4,050
 All these he composed through prophecy which was given him from before the Most High.
3. The Greek tradition goes back at least as far as codex Sinaiticus (4th c), with various editorial transitions:
Some MSS povide a subscription/explicit after Ps 150 specifying the "book of Psalms (+ of David T) 150" (B T) or "Psalms of David 150" (Sa) or "Psalms 150" (1219), but there is no subscription at this point in S R'' Ga He A'. Sy has a decorative divider as also after Pss 40, 71, 88, 108 -- the subdivisions of the Psalter.
Ps 151 is not found in VulgAug ThtHe, and is not written in stichoi in T 55.
The title given in the MSS that include it runs as follows:
This (The Sy) Psalm is an idiograph to/by (of R L\d TSy A) David,
and is outside of the number (+of the 150 Psalms L\d | + nor is it found in all the antigraphoi Sy),
when he fought singled handedly (+against R L\a A') Goliad (Goliath L\dT A') (+ and I found a lion and a wolf and killed them and dismembered them; five additional Sy Pss).
The Greek text and variants (apud Rahlfs' separate edition) are:
[1b] Small was I among my brothers
and youngest in the house of my father;
I tended the sheep of my father.
 My hands made an instrument
(+and L 55) my fingers tuned a harp,
 and who announces to my (the Sa L\pau) lord ? (line not in G\a)
he is lord, he hears (+ from all S La\G Ga| + from all those who call on him | + me Sa\B La\R A | is my God Sy)!
 he sent out his angel (line not in La\R
and took me from (+ the shepherding of L\pau 55) the sheep of my father
and anointed me with the oil (mercy S' R'' Ga L\pau A) of his anointing
 (+Now A) My brothers were handsome and hearty
and he was not pleased with them, the lord (> the lord La\G)
 I went out in confrontation with the foreigner
and he cursed me with his idols
 But I (+beheaded him R' Sy), when I snatched the sword he (that one A) had,
beheaded him (earlier in verse in R' Sy) and removed reproach from the sons of Israel.
Some Greek witnesses add various subscripts here:
Psalms of DAA [sic!] 151 (S)
Book of Psalms (Sa)
Psalms 150 and idiograph one (A)
end of the Psalter (La\ R )
(no subscript here in B R' Ga TSy 55; see after Ps 150)
4. The Syriac tradition includes this material with four other "extracanonical" psalms (for some general information, follow this link). ET adapted from OTP 2:
I was the smallest/youngest of/among my brothers,
and a child/youth of/in my father's house.
I was tending my father's flocks,
[and I discovered a lion and a wolf and I killed and I rent them (in A\mg)]
My hands made instruments [organon]
and my fingers fashioned/fitted lyres.
And who will declare [ptcp] my Lord?
He/that is the Lord, he/that is my God.
He sent his angel
and removed/exalted me from the sheep of my father
and anointed me with the ointment of (his) anointing.
My brothers were handsome and majextic/mature/old
but the Lord did/was not choose/pleased (with) them
I went out to attack/invade the Philistine
and he cursed me by his idols.
But after I unsheathed his sword, (and with it) I cut off his head
and I removed the shame from the sons/house of Israel.
Summary -- the main textual differences: