I have an 8-hour each way weekend commute, so I have an Audible subscription and I also listen to podcasts, especially Freakanomics and Car Talk. About 400 of my 450 miles is on interstates where I can turn my brain off. I can't imagine listening to anything in city traffic, and my bike time is fairly limited (Tu, We, Th, sometimes M), so I don't want to interrupt it!

The 3 months when I listened to the Girl With The Dragon Tatoo books had lots of white-knuckle, full-bladder, can't-stop driving. No good for biking.