To kick us off:
To the man in the street who, I’m sorry to say
Is a keen observer of life
The word “Intellectual” suggests straight away
A man who’s untrue to his wife
W.H. Auden
On the Antiquity of Microbes
Adam
'ad 'em
Anon
Shake and shake the ketchup bottle,
First comes none, and then a lot’ll.
- Richard Armour (I think)
Spot on with that one, Mr MTGuru Sir. 
There must be many more out there. Ones that really get to the heart of life’s little vagaries, profundities amd mysteries, as your example does.
Ogden Nash often hits the nail on the head for me. Here’s one that feels very topical for me at the moment, having to endure a houseful of Mr Annoying Fly and all his friends and relations.
God in His wisdom
Invented the fly
And then forgot
To tell us why
Ketchup, such a silly topic,
Just because it’s thixotropic.
-Emily (I’m sure.)
Does YouTube verse count? Well, here’s one of my all time favs from Charlie Rich http://www.youtube.com/watch?v=6Azui-cs9DQ
or another version from Raul Malo http://www.youtube.com/watch?v=fsRL-vGKRbM
“Life Has It’s Little Ups And Downs”
Oh, that definitely counts, ytliek. 
Listening to Charlie Rich now. Gorgeous stuff.
Mmmmm …
'That’s the way the world goes 'round,
you’re up one day and the next you’re down.
It’s a half an inch of water, and you think you’re gonna drown.
That’s the way the world goes ‘round.’
John Prine
Dream as if you’ll live forever.
Live as if you’ll die today.
- James Dean
Malt does more than Milton can
To justify God’s ways to man.
A. E. Houseman
Gosh! While looking for more inspiration, I’ve come across this site.
Is Wendy Dunning supposed to be famous or something? Does she write greetings cards? I’m sure I’ve heard the name …
Yikes! Now I’m feeling diabetic.
I had a friend, once, who was diabetic. He was sweet.
I RECOMMEND SOFTENING OF THE OUGHTERIES
When I was young I always knew the meretricious from the true.
I was alert to call a halt on other people’s every fault.
My creed left no more chance for doubt than station doors marked IN and OUT.
A prophet with righteousness elated, dogmatic and opinionated.
Once self convinced, I would not budge; I was indeed a hanging judge.
I admitted, in either joy or sorrow, no yesterday and no tomorrow.
My summary of life was reckoned by what went on that very second.
I scoffed when kindly uncles and aunts said age would teach me tolerance.
For tolerance implies a doubt that IN is IN and OUT is OUT.
But now that I am forty-nine, I’m tolerant and like it fine.
Since the faults of others I condone, I can be tolerant of my own.
I realize the sky won’t fall if I don’t pay my bills at all.
The King of Sweden it will not irk to hear that I neglect my work,
And tombfuls of historic dead care not how late I lie abed.
Oh, tolerance is the state of grace where everything falls into place.
So now I tolerantly think I could tolerate a little drink.
Ogden Nash
Nice one, trill. I didn’t know that one. 
Reminds me of one of my favourite tea mugs, which reads:
“I am not young enough to know everything”
Once I’d dropped callow black-or-white
A scare came to me in the night:
As life is sweet as it is ruthless,
The cynic says that life is truthless.
If all is chaos, and certainty madness,
Then what’s the harm in leaving sadness?
So kiss this fool, you fool. And soon
Let us go, and share the moon.
- Nano
When you were one-and-twenty …
He hits it for me as well. This has long been one of my favorites. How can you fail to appreciate someone who can rhyme “lapis lazuli” and “casually?”
Let George Do It, If You Can Find Him
Ogden Nash
from A Penny Saved Is Impossible (1981)
The wind comes walloping out of the West,
And the sky is lapis lazuli,
And the hills are bold in red and gold,
And I cannot take it casually.
Oh, cruel day for a man to spend
At counter or desk or forge!
I think I shall stray from duty today,
And turn it over to George.
George! George! Where are you, George?
Clear the air for a call to George!
There is work to be done, dear George,
And fame to be won, dear George!
There are words to write,
And columns to add,
And everyone says
That George is the lad.
Here is a pen and here is a pencil,
Here’s a typewriter, here’s a stencil,
Here is a list of today’s appointments,
And all the flies in all the ointments,
The daily woes that a man endures –
Take them, George, they’re yours!
I will arise and roam the fields
Where edible coveys flutter.
I will conquer, methinks, the perilous links
With a true and deadly putter.
I’ll forsake the grime of the city street
For valley and hill and gorge;
I will, or I would, or I shall, or should,
But I can’t get hold of George!
George! George! Where are you, George?
Come out from under the sofa, George!
I thought you were braver, George!
I’m doing you a favor, George!
You can use my desk,
And sit in my chair,
Snugly away from the nasty air.
Safe from the other fellow’s cartridges,
Safe from returning without any partridges,
Safe from treacherous spoons and brassies,
And the flaming shorts of the golfing lassies.
All this, dear George, I am trying to spare you.
George! You softie, where are you?