As it turns out, the Psalms are hard to write about. I find them easier to just soak in than study, although I've run across several passages that could certainly benefit from study.
One benefit that I've discovered of "soaking" in the Psalms is that I start to pray like the Psalms. They are such a comprehensive expression of human experience that they really need no updating. Who hasn't cried out to God in pain, asked where He was in a trial, praised Him joyfully in abundant blessing? The Psalms assure you that these are not novel experiences, but a normal part of the life of God's people.
A few highlights which I have found especially helpful:
So teach us to number our days, that we may get a heart of wisdom.
Return, O Lord! How long? Have pity on your servants!
Satisfy us in the morning with your steadfast love, that we may rejoice and be glad all our days.
Make us glad for as many days as you have afflicted us, and for as many years as we have seen evil.
Let your work be shown to you servants, and your glorious power to their children.
Let the favor of the Lord our God be upon us, and establish the work of our hands upon us; yes, establish the work of our hands!
I'm not sure exactly what to do with it, but I think that the entirety of Psalm 90 merits some very close study. One thing that makes it hard (for me) to study the Psalms is that many of them seem disjointed, jumping from one topic to another with nary a word by way of transition. Psalm 90 is not like that. It is very thematic, dealing with the passage of time: how we experience it and how God does, how it is a gift and how we ought to use it wisely. I get the feeling that there is a lot there, lurking under the surface. Teach us to number our days, that we may get a heart of wisdom. I don't know what that means, but I want to.
Unless the Lord build the house, those who build it labor in vain.
Unless the Lord watches over the city, the watchman stays awake in vain.
It is in vain that you rise up early and go late to rest, eating the bread of anxious toil; for he gives to his beloved sleep.
Behold, children are a heritage from the Lord, the fruit of the womb a reward.
Like arrows in the hand of a warrior are the children of one's youth.
Blessed is the man who fills his quiver with them!
He shall not be put to shame when he speaks with his enemies in the gate.
This is a famous Psalm, and I was already aware of most of its contents. But I didn't quite realize how it cohered. The first three verses can be applied to just about anything, but I think that in the context of the latter verses it is speaking metaphorically of the work of building a home. Unless the Lord build my family and watch over it, I labor in vain. I know this, of course, but Pelagianism is a pernicious heresy. I often catch myself sucumbing to it even when I know better.
This verse also really struck the overworked student in me: It is in vain that you rise up early and go late to rest, eating the bread of anxious toil; for he gives to his beloved sleep. If the Bible is the word of God, then this is really true. Test it. Lay your workload at the feet of Jesus and go to bed. God giveth the increase, not your effort - no matter how many hours you work. Unless the Lord do the homework, they labor in vain who caffeinate themselves.
For I was envious of the arrogant when I saw the prosperity of the wicked.
For they have no pangs until death; their bodies are fat and sleek.
They are not in trouble as others are; they are no stricken like the rest of mankind....
But when I thought how to understand this, it seemed to me a wearisome task,
Until I went into the Sanctuary of God; then I discerned their end.
Truly you set them in slippery places; you make them fall to ruin.
How they are destroyed in a moment, swept away utterly by terrors!
This Psalm is fascinating as a window into the author's outlook and how it changes in "the Sanctuary of God." I think I can hear a hint of a reference to the afterlife in the final end of the wicked. The author is looking with different eyes when in the house of God. He does not just remember calamities that he had forgotten before. He understands what it means to live well in a different way - a way that is, I think, less focussed on the external metrics of worldly success and more on what it means to be truly, fully satisfied.