Psalm 2 - Why do the nations proudly rage?
The next step in the Christian life is to see the world for what it is, in contrast to Christ for what He is.

The world is the enemy of Christ and God. Christ is the real Possessor of everything good, and the One to fear, and how blessed it is to trust in Him.

"How would Christians cease to look to the governments of the earth and to national enlightenment and progress, as the pillar on which they rest their hopes for the earth's future, if they received the words of Joel, and Zechariah, and of this Psalm!" - Benjamin Newton
vv 1-3 refer to Christ's being persecuted in His incarnation and human life (Acts 4:25-28).  
According to the verses in Acts 4: "The nations" (Hebrew goim) refers to the Romans. "The peoples" (Hebrew lumim) refers to the groups of people within Israel, i.e. the Sadducees, Pharisees, and Herodians. The kings and rulers refer to Herod and Pilate.
v4 - The Lord shall laugh at them because they have accomplished His purpose in killing Christ. (1 Cor 2:7-8)
v5 - "Then" means "after this". The Lord, Christ, will speak to these rebellers against His yoke in anger when He returns.
v 6 "poured out" refers to Christ's laying down His life for us (2Tim. 4:6 referring to Paul's martyrdom). "Poured out" is the most literal translation of the Hebrew word, nasach. KJV translated it as "set" which it does not mean. Darby & YLT translated it as "annointed", which it also does not mean.

The word "I" is emphatic in the Hebrew. The meaning is "I, Myself" or "I, even I".  Even though the rulers of this age put the Lord to death, it was actually God Himself who did it (Isa 53:10).
v 7 - "This day have I begotten Thee" refers to the Lord's resurrection. (Acts 13:33)
v 8 - God tells the Messiah to ask for 2 things:
1) the nations for Your inheritance
2) the uttermost parts of the earth for Your possession

The nations who are the Messiah's inheritance are the Gentile Christians. It is a great thing for the Gentiles to be the Messiah's inheritance! His inheritance is the most valuable thing He owns (1 Kg 21:3; Ps 127:3;136:21-22; Eccl 7:11). Throughout the Old Testament, Israel is repeatedly called the Lord's inheritance, especially in the Psalms. (Isa 19:25; Exo 34:9; Deut 9:26, 29; etc.) These are those Gentiles and Jews who believe into Jesus during the church age. They become His inheritance (Eph 1:11-12,18). The Gentile Christians are to be joint-heirs of God with Israel (Eph 3:3-6).

The uttermost parts of the earth also refer to Gentiles, but these are the millenium Gentiles, who are different from Christians. These are the nations who are judged to be righteous at the Lord's return (Matt 25:32-40).
The Messiah will possess the uttermost parts of the earth at his coming back (Rev 11:15).
In all the Old Testament Prophecies concerning the Messiah, there is this 2,000 year gap between His 1st and 2nd comings.
v9 - When the Lord returns, He and His overcoming saints will shepherd the nations in the uttermost parts of the earth with an iron rod.  (Rev 19:15; 2:26-27; 12:5). These nations are not Christians, but righteous Gentiles. This will be during the millenium and then the new heaven and new earth (Rev 15:3-4; 20:3; Zech 14:16-19; Rev 20:7-8; 21:23-26; 22:2).  
vv10-12 - These are good instructions for the rulers  and judges in exercising their earthly authority:
1. Serve the Lord with fear
2. Rejoice with trembling
3. Kiss the Son lest He be angry
4. Trust  the Son

A Christian kisses the Son because he loves Him because He gave up His life for us. But a political leader kisses the Son lest He be angry.

The word for "Son" here is bar, not the usual word, ben, which is used in verse 7. Bar is the Aramaic equivalent to the Hebrew word, ben, and is used in the Aramaic parts of the Old Testament just as ben is used in the Hebrew parts (Ezra 5:1;  etc). Bar is also used in the Hebrew of the Old Testament in Prov 31:2.
It is hard to say why bar is used here rather than ben. It may be that bar is used because Gentile rulers are addressed. The only other place in the Hebrew part of the Bible that uses the word bar,  Prov 31:2, was written by King Lemuel, who apparently was a wise Gentile king. Leupold points out a possibility that in the poetry of the Psalm, bar may have been used in order "to avoid the dissonance of ben pen". (Pen is the Hebrew word for "lest", which immediately follows the word for "Son".)
Luke 19:14  But his citizens hated him and sent an envoy after him, saying, We do not want this man to reign over us.
Acts 13:33  That God has fully fulfilled this promise to us their children in raising up Jesus, as it is also written in the second Psalm, ``You are My Son; today I have begotten You.''
Rev 2:26-27  And he who overcomes and he who keeps My works until the end, to him I will give authority over the nations;  27  And he will shepherd them with an iron rod, as vessels of pottery are broken in pieces, as I also have received from My Father;
Rev 12:3-5  And another sign was seen in heaven; and behold, there was a great red dragon, having seven heads and ten horns, and on his heads seven diadems.  4  And his tail drags away the third part of the stars of heaven, and he cast them to the earth. And the dragon stood before the woman who was about to bring forth, so that when she brings forth he might devour her child.  5  And she brought forth a son, a man-child, who is to shepherd all the  nations  with an iron rod; and her child was caught up to God and to His throne.

-Steve Miller updated 5/3/09