Almost exactly one year ago, we
pointed you to
AudioBooksForFree. It looks like they're alive and well, and they continue to add books. The web site is a bit busy, but it's enough to get you to the audiobooks.
Previously, most of their books were machine read. Don't know if that's still true, but it does look like they have a lot of books there.
Maybe a better source is the
Gutenberg project, which also has audio books available for free, some by machine readers and some by human readers.
And don't forget that almost any pda with a memory card can hold and play mp3s. Add a car adapter kit, you can listen to these audiobooks on your car's audio system while you commute. (Any electronics store has car adapter kits for about $20 that connects to your pda's headphone jack to a cassette deck or broadcasts FM radio).