Today's poem is one I found on a site called Poetry 180. The site offers one poem for every school day. This first poem is the first in the series, and I think makes an excellent "introduction to poetry."
Introduction to Poetry
by Billy Collins
I ask them to take a poem
and hold it up to the light
like a color slide
or press an ear against its hive.
I say drop a mouse into a poem
and watch him probe his way out,
or walk inside the poem's room
and feel the walls for a light switch.
Go here for the rest of the poem.
Here are some links for audio recordings of Billy Collins. I recommend the Library of Congress video, but you can skip the first 5 minutes of introduction.