Technically, Bill DeSmedt's Singularity probably should get classified as an audio book. Professional narration of a novel doesn't quite meet my notion of a podcast. Still, the work is available on Podiobooks.com as an iTunes compatible or RSS podcast feed. For free too (with a suggested donation).
I started listening to the book on my last trip to Corpus Christi. It worked great. The fast pace and nearly constant excitement made the four hour drive go by in a flash.
The book is science fiction, but think Robert Ludlum meets Michael Crichton. Events hinge on speculative science, but it mostly occurs in the near future (well, the past's near future... the 1990's) with plenty of explosions and fights. It's full of crazy science, but most of it explained so that a layman can follow easily.
There are some anachronisms in the novel. Technology evolved a little differently in our future than what was expected when the book was written. Some of the computer science and hacking stuff seems a little off too. Still, it's worth cutting the book some slack.
And that professional narration? It seems to have been done by the author personally. Color me impressed. The accents and voices are all done quite well -- I swear he sounds like a professional narrator. Link.