I have eaten
that were in
you were probably
they were delicious
and so cold
--William Carlos Williams
They had me read it three or four times, they thought it was so funny. The simplicity tickled them, and they enjoyed the wording, especially "and so cold."
We also read Oliphaunt (at the bottom of that link) by J. R. R. Tolkien and The Road Not Taken by Robert Frost.
The Farm School post lists a bunch of poetry sites and talks about the poem "Keep A Poem in Your Pocket." Periwinkles and Pines has a cute poetry post on clouds, including a few other poetry links.