Another favorite of mine in the audio realm: Lemony Snicket's A Series of Unfortunate Events as narrated by Tim Curry. Several of the books in this delightful series have been narrated solely by the author (Lemony Snicket) and, frankly, they're not as good as Curry's renditions.
This series lends itself well to audio format because there's a great deal of authorial intrusion (when the author breaks from the plot to tell the reader something specifically; in the SOUE books, this happens most often when the author tells the reader what a word means). Curry's narration makes this authorial intrusion come alive. His wry sense of humor comes through and his inflections and emphases are perfect. The books are quite funny on paper; in audio format, they're hilarious. There is also some rather weird, but fitting, music at the beginning and, occasionally at the end, an "interview" with Lemony Snicket himself. Highly recommended for road trips and boring house work.