A problem with our hearing of Psalm 8, as with so many other biblical texts, may be our affluence.
Most of us are so used to being more or less well off and more or less comfortable that we have difficulty hearing the text from the margin, from the perspective of the underdog or the endangered. The result is not only confusion, but potentially destructive misuse.
The issue in Psalm 8, as in Genesis 1 to which it refers, is the relationship between humanity (us!) and the rest of creation. The psalm sings the old creation story into the present, rejoicing again in being made "little less than divine" (NJPS), which means having "dominion" over the works of God's hands, over all creation. Creation is not merely a one-time act "in the beginning," but an ongoing work and gift of God that makes us realize ever anew "how majestic is your name in all the earth."
The problem, as we have heard often, is that one generation's "dominion" becomes a later generation's exploitation, and woe to the earth and woe to us if we think the psalms gives us license to do whatever is now in our power to ravish the earth and use up its resources. If this creational dimension of the psalm becomes a part of our preaching, we need to make people hear as clearly as possible that exploitation is not the message of Genesis 1 and not that of Psalm 8.
We live in a different world from that of these texts. When singers of the psalm looked "at your heavens, the work of your fingers, the moon and stars that you have established," they saw not the many stars and galaxies light-years away that we know from our science classes, planetariums, and telescopes, with the earth a mere speck in a minor planetary system, but the stars and the moon as fixed points on a half-dome sky, surrounding an earth that was the center of the universe, indeed, that was the universe. Even so, they were overwhelmed by the grandeur! And we? We may be all the more awed by our expanded sense of universe, giving greater praise to God, or some of us might find the notion of God quaintly irrelevant given our "greater" understanding.
Similarly, when the psalmists rejoiced in their surprising ability, under God, to bring sustenance from an unwieldy planet, they lived in a time when such "dominion" was relatively new--the ability to domesticate animals and till the soil--and the alternative was a daily hunter-gatherer existence that gave little or no time for developing culture, civilization, or even communal worship. "Praise the Lord," they sang, "for God has blessed our humble efforts and given us life!"
But we dare not say, "Praise the Lord, for God has blessed all the assaults on the earth of which we are now capable and given us bigger and better stuff." We too rightly rejoice in God's blessing of our works, but, to be blessed, such works must understand "dominion" in the sense of Psalm 72, where the purpose of royal dominion (Psalm 72:8) is to "defend the cause of the poor" (verse 4) and to bring "abundance" (verse 16), "righteousness" (verse 7), and "peace" (verse 7) to all. That work is worthy of praise!
There are many potential sermons on Psalm 8, of course, as with any text. One will be to rejoice in our exercise of the responsible dominion given us by God as creatures who are "little less than divine" (a better translation than NRSV's "a little lower than God"). Amazing! We rejoice in the gift, even as we pray for humility to bear the responsibility of exercising anything resembling god-like power over the earth. We have power, to be sure, but God-like power will abuse nothing.
Another sermon derives simply from the poetic structure of the psalm. A modern, Western reading of the psalm tends to focus on the question "What are humans that you are mindful of them?" as an outburst of existential anxiety from an "I" alone in the midst of overwhelming vastness. There might be something in that, but the structure of the psalm puts the singer in a different place. Psalm 8 has a rather clear concentric structure:
A O Lord, our Sovereign... (verse 1a)
B You have set your glory... (verses 1b-2)
C When I look... (verses 3-4)
B' Yet, you have made... (verses 5-8)
A' O Lord, our Sovereign (verse 9)
The A/B/C/B'/A' structure is, in part at least, grammatical or rhetorical, comprised of sections introduced by Lord/you/I/you/Lord.
The psalm begins and ends with the outburst of congregational praise of God's majestic name (A/A'). Within those verses comes the praise of God's particular works (overturning foes in B; blessing humans in B'), and, at the center, the wondering awe of the poet (C). Now, instead of an isolated "me," viewing a distant universe in existential anxiety, "I" (C) stand surrounded by the gracious and protecting works of God (B/B') and the congregation gathered to sing God's praise (A/A'). (This structure of the psalm could be modeled for the congregation by reading or singing it in worship in three groups: A, B, and C, corresponding to the segments of the psalm.)
Now, the answer to the singer's question "Who am I?" question is the surprised recognition that "I'm surrounded!"--which could well be the title of a sermon on this psalm. "I'm surrounded!"--surrounded by the gracious works of God and the gathered community of God's people. It is a good and safe place to be; a place where I am not left to my own devices to figure out who I am, but am given a place in relation to God, to God's world, and to God's people; a place where my identity is given (not my own project) and where I am kept safe from whatever "foes" (verses 1b-2) stand in opposition to God's good will for me and all God's creatures.