I recently found a very fun reimplementation of UNIX cat that adds OS X's capability for speech synthesis. The binary is available from gnufoo.org. To install, place the file in ~/bin and run chmod -x ~/bin/cat to make it executable. There's also a patch for the system-wide cat available.
Then run ~/bin/cat -a and type something. Hit return, and your Mac speaks the text back to you. Or give it a filename, i.e. ~/bin/cat -a tellmeastory.txt and the machine will read you its contents. Since it would be easy to call the 'talking cat' from a shell script, there are possibilites for spoken error messages and the like.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2002100806572753