Besides writing limericks, I have also translated Die Lorelei by Herman Hesse. We read this poem in my German class, back in high school or college, and I have never been really satisfied by any of the translations.

I decided that maybe the problem was that there wasn't really enough space in English to translate it properly if you used the same meter as the original. So I decided to try to translate it into ballad meter:

I do not know the reason for
     This sadness that's come over me.
A fairy tale from the days of yore
     Racks my mind ceaselessly.
...
A funny thing happened when I was translating it, though. I figured out how to translate it using the original meter, and ended up with a version that I like much better than my ballad version. Without further ado, here it is:
            The Lorelei

         Herman Hesse
I don't know why I am feeling
     So sorrowful at heart.
An old myth through my thoughts is reeling,
     And from them will not depart.
The cool evening air makes me shiver
     As I watch the Rhine's gentle flow.
The peak towering over the river
     Gleams bright in the sun's setting glow.

Up high on a ledge is sitting
     A maiden most marvelously fair.
Her golden jewelry is glitt'ring.
     She is combing her golden hair.
She uses a gold comb to comb it.
     And sings a song as well,
That echoes down off the summit
     And casts a melodic spell.

The boatman is seized by wild yearning
     While guiding his small craft downstream.
His eyes from the rocks ahead turning,
     He looks up, lost in a dream.
I fear that the boat and her master
     Will soon underwater lie.
And what brought about this disaster?
     The song of the Lorelei.