Leopard has a new text to speech voice, Fred. Fred has an issue, he never ever shuts up. Open up the speech preference pane, and assign a hot key so you can tell any selected text to speak out loud. I used control-T. It works amazingly well. With a small bump in the speaking speed, you can kick back and do other things while Fred is reading to you.

The rub? He never stops, and as far as I can tell, there is no way to make him stop talking. Select with caution, if you select an entire book of text, your computer will be talking to you for days on end. The only way I have found out of this is a logout. Maybe a force quit on Finder would do it as well.