Librivox is a project for free audiobooks read by human volunteers from public domain texts.
The quality of the voices vary, but the best thing about it is that you can look at the source text over at Project Gutenberg first, to see if the vocabulary/complexity suits you, and then download the audiofile to accompany it. When you're not driving, you can read-along as you listen, or maybe just check the text after listening to see how much you understood.
They've got a range of material: fiction, non-fiction, essays, short stories, children's, plays; should be plenty of stuff to provide a good variety of practice listening.