I used to use ispeakit, but decided I didn't want to pay for an upgrade. So after doing a google search I found "Automator" in my own app folder. I found an article showing how to make a simple plug-in within automator that converts text to speech or audio file.
Turn text into audio
You can put this into itunes or on your ipod or iphone. Just double click the file and it's in itunes. Works for when you want to listen to something instead of read it. Or when your not able to read, but can listen. Or just write your own audio book.
You can find the automator workflow plug-ins under users-home folder-library-workflows-applications-finder folder.
I made a new folder in my documents called "audio books" for saving when using automator. Then put the folder in the side bar for easy access.
Here is another Script writer for doing the same thing and more. Jon L
Charles Kelly's Macintosh Page: Text to speech.