Verbalize... You may already know your Mac can talk. But how do you make it say exactly what you want? There have been a few different alternatives, but Verbalize is the most straightforward and easy-to-use application around. Plus it has really good looks!
Version 6.1 has the ability to utomatically create audiobooks from your text. It also adds a new multi-line view and using Remote Apple Events, you can speak directly to another computer on your local network.
Mac OS X 10.4 or later