I have never listened to an audio book before and since I would like to do some more walking, I feel that audio books would be good motivators to get me going and entertain me. Are there audio books you really appreciated or felt were really well done?

I really like the Dresden Files audiobooks. Read by James Marsters (aka Spike from Buffy).

I like any mystery audiobooks...

Some authors I like are:

Jeffery Deaver
Agatha Christie
Carolyn G Hart
Diane Mott Davidson
Laurie R King
Elizabeth Peters
Kathy Reichs

They sure make the time go by faster!

I like Janet Evanovich's Stephanie Plum series on audio.

the Pink Carnation Series by Lauren Willig is fun on audio too. Also I love the Amelia Peabody series by Elizabeth Peters, make sure to get the ones read by Barbara Rosenblat, as she does great with the voices. And of course Diana Gabaldon's Outlander series, read by Davina Porter, again she does better with voices and accents than the other reader they've had.

I have a lot of favorites, since I've been a member of audible.com for about 4 years now! but you should hopefully be able to find them at the library also.

I have so many -- I really like to listen to Stephen King's books on audio. Also Dean Koontz (they are scarier that way, lol). Heart Shaped Box by Stephen king's son Joe Hill is awesome on audio.

I am currently listening to Garth Nix's Abhorsen series on audio and Tim Curry is the reader.

I think people already mentioned Diana Mott Davidson & Janet Evanovich's books on audio. Also, Sue Grafton's books are very good.

I recently listened to "A Dirty Job" by Christopher Moore on audio and loved it.

Podcasts of American Life from NPR are great to listen to also.

I like a lot of the British full cast productions of old murder mysteries like Agatha Christie or PD James.

Garrison Keillor's Prairie Home Companion series on audio is great.

If you like fantasy -- Robert Jordan's Wheel of Time series in unabridged audio is outstanding. Also the Harry Potter's unabridged.

The reader makes a very big difference in whether I like an audio or not.

Some of my favorite readers are:
George Guidall
CJ Critt
Tim Curry
Kate Reading
Loreli King

The list goes on and on. I've listened to audiobooks now for well over 10 years and have greatly enjoyed having someone read to me, lol.

There are some series that once I listened to the first book in audio (unabridged CDs) I just couldn't get into the text version. Conversely, having read a book in text, I can't bear to "read" a sequel with audio.

Audio books I've enjoyed:

Janet Evanovich: Metro Girl and Motor Mouth in the Alex Barnaby series
David Baldacci: Split Second and Simple Genius starring Sean King and Michelle Maxwell
Alexander McCall Smith: The Sunday Philosophy Club, Friends, Lovers, Chocolate, The Right Attitude to Rain, andThe Careful Use of Compliments in the Isabel Dalhousie series
Alexander McCall Smith: 44 Scotland Street and Espresso Tales in the 44 Scotland Street series
Nicholas Sparks: Nights in Rodanthe and True Believer

I listen to a lot of audio books and tend to like mysteries. I also find that it's fun to liste to classics that you might not read otherwise. I loved Les Miserables for example, but don't think I'd have picked up the book.

I usually listen to 2-3 audiobooks per month because I'm in the car a lot for work. (usually borrow them from the library) I'm very addicted! I often think sometimes I love books more just because the reader did an exceptional job, and don't know if I would've loved the book so much in just the written form. (But on the other hand, some readers are not as good, and that can take away from the enjoyment.)

I just today finished The Confessions of Max Tivoli on audio and absolutely loved it! That one was read by Brian Keeler, who did a great job.

I agree with shaunesay....Davina Porter is a very good reader too. She was awesome in Outlander and she's also done several of Philippa Gregory's books.

Scott Brick is also one of my favorite readers. I've read several audios with him, my favorite being The Shadow of the Wind. (at least I'm pretty sure he did that one)

I also like George Guidall as a reader. He does the introductions on a lot of the audiobooks, but also read on Wally Lamb's I Know This Much is True, which is also one of my favorites (but very long!).

And I've never actually listened to any of the Harry Potters on audio, but everyone raves about the guy who reads those, Jim Dale.