If you'd like to take any block of text and have it easily transferred as spoken text to your iPhone or iPod, I found this feature is now built in to Snow Leopard as a Service.
To use this feature, first enable it in System Preferences » Keyboard » Keyboard Shortcuts » Services. In the left-hand column, select Services, then scroll down to the Text section in the right-hand window and enable 'Add to iTunes as a Spoken Track.' Add a keyboard shortcut, too, if you wish by clicking in the space adjacent to this services' name.
Now whenever you have a block of text highlighted, Control-click on it and choose Add to iTunes as a Spoken Track from the pop-up menu. Alternatively, you can press your defined keyboard shortcut, or get to the command from the Services menu item. The quality of the speech is quite acceptable!
[robg adds: Yes, this is a built-in command, and we don't normally hint such things, but in a quick survey I just took, nobody had realized this was here. This greatly simplifies the task of converting text into audio form - it basically replaces this hint, which created a Service in 10.5. (There's also this hint, which creates audiobooks from PDFs.)]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20100218202557991