I have no idea where I first saw this poem. It was first posted to Usenet in 1992... but I only started reading Usenet in 1994. I remember spending a long time searching for it again, and finding it again and reading it again... and then losing it again.
So here it is. Note that it is freely distributable, as long as we "give credit where credit is due", which is functionally equivalent to CC-BY.
CASEY AT THE WYRM
[sorry, but a careful analysis of the original poet's release notice indicates that it's not sufficiently equivalent to CC-BY, sigh. So the poem is no longer available here — good thing I kept track of the provenance. Anyone who still wants 'Casey at the Wyrm' can just follow the above link to the archived Usenet post.]
"Sharded stumps."