Robert Pinsky proposes one that is, interestingly enough, decades old and written by a Brazilian. Click here to read the poem--"Souvenir of the Ancient World" by Carlos Drummond de Andrade--and Pinsky's brief, clear explication of it. Or click here to read the poem without the commentary.
Pinsky nominated the poem for Slate's collection of art that helped make sense of 9/11; he also found some solace in a "table read" of a script for The Simpsons he was invited to on September 12, 2001, having been stranded in Los Angeles when air travel was suspended. Read about the experience here.