The only real shout-outs in Holes come from the poetry that Miss Katherine and Sam share while he is working on the schoolhouse (25.25). It's pretty sweet stuff. The book mentions two poets in particular, Edgar Allan Poe and Henry Wadsworth Longfellow.
Longfellow wrote lyric poetry, often drawing his subject matter from mythology and legend. Poe, who is probably best known for his disturbing short stories and for his poem "The Raven" (of "Nevermore" fame), often wrote tales of heartsick lovers haunted by the death of their beloved – a little foreshadowing, anyone?
Just to give you a taste of the kind of thing we're talking about, here's a passage from Poe's poem "Annabel Lee." (Bonus: this is the poem that Miss Katherine and Sam recite to each other in the movie version of Holes.)
For the moon never beams without bringing me dreams Of the beautiful Annabel Lee; And the stars never rise but I feel the bright eyes Of the beautiful Annabel Lee; And so, all the night-tide, I lie down by the side Of my darling – my darling – my life and my bride, In the sepulchre there by the sea, In her tomb by the sounding sea. (lines 34- 41)