Anyone know an app that will read writing aloud?

TextEdit will do it, under edit--speech.

Then you could use Audio Hijack to convert it to an MP3.

But why not just record yourself reading the poem?

 

I think it'd be better if you did it, or if you don't want to hear your voice, got a friend to do it, too, because it will be natural. Do not expect the speech synthesizer to nail the meter!

 

Use this free AppleScript

http://www.apple.com/applescript/macosx/text2audio.html

Choose the voice that you want to hear.
Open and select all the text in TextEdit.
Run the script and it saves the spoken result into an .AIF file

You can then import it into iTunes in the format of your choice.

Works extremely well and with some extra tags in the text, you can even add pauses, emphasis and change intonation.