I must admit that I have never been a big audio book fan before I had children. I am a very visual person, and I much prefer reading a book than listening to one. When I had children, however, I quickly found the benefits of audio books. I have read aloud to my children from birth (or before), and they are used to listening to books- long, chapter books. There are times when reading aloud is just not practical: driving in the car, eating a meal, or when I'm just tired. So, I discovered the joys of audio books. And, I have found many that I have enjoyed as much as my children- especially on long car trips.
Some of our favorites have been:
The Famous Five books by Enid Blyton
The Secret Seven books (also by Blyton)
Mrs. Piggle Wiggle by Betty Macdonald
The Penderwicks by Jeanne Birdsall
Story of the World Volume One by Susan Wise Bauer
Very closely related to audio books are radio dramas. My children love to listen to radio dramas. We find lots of good ones at HisKids.Net.
There are also some good radio programs for kids and adults at Oneplace.
On these two sites, we can listen to The Pond, Paws and Tales, Adventures in Odyssey, and Your Story Hour.
To find good audio books, you usually need look no further than your library. Our library has a very good selection. Some libraries are also registered through NetLibrary, which allows you to download audio books to your computer and MP3 player just like checking them out through the library. You can use their library selector to see if your library is registered. LibriVox has great free audio books for adults and children to listen.
I plan to stock up on CDs from the library and MP3s from NetLibrary for our beach trip this summer!