First encountered this when I was teaching English in Japan

And it reminded me how freakin' hard English is to learn, so I was more sympathetic to my students.

I take it you already know
Of tough and bough and cough and dough?
Others may stumble, but not you,
On hiccough, thorough, lough and through?
Well done! And now you wish, perhaps,
To learn of less familiar traps?
Beware of heard, a dreadful word
That looks like beard and sounds like bird,
And dead: it's said like bed, not bead -
For goodness sake don't call it deed!
Watch out for meat and great and threat
(They rhyme with suite and straight and debt).

A moth is not a moth in mother,
Nor both in bother, broth in brother,
And here is not a match for there
Nor dear and fear for bear and pear,
And then there's dose and rose and lose -
Just look them up - and goose and choose,
And cork and work and card and ward,
And font and front and word and sword,
And do and go and thwart and cart -
Come, come, I've hardly made a start!
A dreadful language? Man alive!
I'd mastered it when I was five!

Got this in an email today

We must polish the Polish furniture.
He could lead if he would get the lead out.
The farm was used to produce produce.
The dump was so full that it had to refuse more refuse.
The soldier decided to desert in the desert.
This was a good time to present the present.
A bass was painted on the head of the bass drum.
When shot at, the dove dove into the bushes.
I did not object to the object.
The insurance was invalid for the invalid.
The bandage was wound around the wound.
There was a row among the oarsmen about how to row.
They were too close to the door to close it.
The buck does funny things when the does are present.
They sent a sewer down to stitch the tear in the sewer line.
To help with planting, the farmer taught his sow to sow.
The wind was too strong to wind the sail.
After a number of injections my jaw got number.
Upon seeing the tear in my clothes I shed a tear.
I had to subject the subject to a series of tests.
How can I intimate this to my most intimate friend?
I read it once and will read it again
I learned much from this learned treatise.
I was content to note the content of the message.
The Blessed Virgin blessed her.
It's a bit wicked to over-trim a short wicked candle.
If he will absent himself we mark him absent.
I incline towards bypassing the incline.

Try reading these aloud. It's tough!

For more of these (and these too), check out this page from the Spelling Society.