As long-time readers know, I'm an enthusastic advocate of Audible.com, a web site that sells audio books in digital format. I initially joined because they had unabridged versions of Atlas Shrugged and The Fountainhead, but I've stayed on becasue of their continuously expanding speculative fiction library.
The latest two additions are George R.R. Martin's Game of Thrones and A Clash of Kings, two epic books that weight in at 35 hours a piece.
As a commuter who listens to books every day, I'm primarily interested in unabridged books that are longer than 15 hours (preferably 20). To find two fantasy novels that add up to 70 hours worth of listening is a freaking gold mine, especially since I've heard nothing but good things about Martin's work. I had considered buying the print versions of the books and trying to slowly work my way through them (attempting to read with a 11-month-old "helping" is difficult at best) but this is far better.