I haven't driven in years, but I listen to audiobooks on my iPod while I'm commuting on the subway or walking. They're good for cleaning the house, too. I think a subscription to Audible is pretty reasonable, but then I review audiobooks, so I get all of mine for free. :-) If you're looking to rip CDs to put on an iPod and you have a Mac, I recommend a $10 piece of software called Audiobook Builder, which compresses the MP3s into audiobook files.
I know the pace of audiobooks is slower than reading, but I think the focused attention you have to pay to an audiobook can make the experience more intense than reading it. Voices can also add a layer of meaning to the audiobook--for example, accents can indicate a character's place in society. Or having Wil Wheaton narrate REDSHIRTS (which is a deconstruction of STAR TREK) adds a whole level of meta to the book.