I own two audio books. William Gibson's Neuromancer and Steve Martin's Pure Drivel, both unabridged, both read by the author. Pure Drivel is great. They added sound effects and stuff, and there's nothing like Steve reading his own material. And listening to William Gibson's weird South Carolinian/Canadian drawl reading science fiction is almost as weird as listening to Isaac Asimov's thick Brooklyn drawl doing the same thing.

Anyway, they're both on my empeg now, and they're remarkably entertaining. You might also want to consider the radio version of H2G2 and the Star Wars trilogy (as a bonus, no Jar-Jar!). And the Lord of the Rings production is great, too.