Psalm 8 is a praise song, and it's kind of nice to read after several psalms that deal with desperation and pain. Verse 1 is something I've seen emblazoned on a lot of Christian merchandise, and it's a really beautiful idea. God is excellent, not in the normal conversational sense of "really great and cool" but in the sense that he excels everyone and everything. His glory is above the heavens; here, I think the speaker is talking about the earthly heavens, a.k.a. the sky and atmosphere.
Verse 2 contains another familiar phrase "out of the mouth of babes," which is usually intended to mean that someone young has said something wise, but here it seems to relate to military strength, somehow.
Verses 3-8 are all one connected thought. When the speaker thinks of all that God has created, including the heavenly bodies like stars and planets, it's hard to understand why God even takes notice of people or cares about them. What are we, compared to the vast beauty (and terror) of the universe? But still God is "mindful" of us and "visits" us. We are important to him, and he devotes his thoughts and time to us.
In fact, verse 5 says that humankind is created to be only "a little lower than the angels". This is really interesting to me. I've always found it amazing that humans are somewhere between animals, which have life but no eternal soul, and angels, which have a celestial existence but (as far as I can tell from Scripture) no free will. We are a peculiar mix of the beastly and celestial.
Verse 6 uses an interesting word, "dominion," to describe humans' control over the earth. We're not just the dominant life form by accident--God gave the earth to us to rule and administrate, so we are responsible for its care. Verse 9 resonates with verse 1 by repeating the phrase about the Lord's excellence.
1O Lord, our Lord, how excellent is thy name in all the earth! who hast set thy glory above the heavens.
2 Out of the mouth of babes and sucklings hast thou ordained strength because of thine enemies, that thou mightest still the enemy and the avenger.
3 When I consider thy heavens, the work of thy fingers, the moon and the stars, which thou hast ordained;
4 What is man, that thou art mindful of him? and the son of man, that thou visitest him?
5 For thou hast made him a little lower than the angels, and hast crowned him with glory and honour.
6 Thou madest him to have dominion over the works of thy hands; thou hast put all things under his feet:
7 All sheep and oxen, yea, and the beasts of the field;
8 The fowl of the air, and the fish of the sea, and whatsoever passeth through the paths of the seas.
9 O Lord our Lord, how excellent is thy name in all the earth!