I've said a number of times that I'm a huge fan of audio books.   I've given you a couple of sites in the past related to this, including some free stuff.

This week I'm revisiting that topic (as I'm sure to do any number of additional times).   I'm also adding "e-books" to this crusade.   As long as they are free.

 
Project Gutenberg is a site dedicated to free exchange of information and culture.   I believe everything on this (not so user-friendly) site is from material with expired (read: old) copyrights.   So if you want to hear the "classics" or read them on your PDA, this is the site for you.
 
It certainly is not the end all or be all of electronic media, but it does serve as a good depository of interesting and free material.