I now work from home, so my commute is approximately 5 seconds. Occasionally I'll go work from a coffee shop to break up my day, but I'm quite content being home. Prior to this, I've had commutes that ranged from 20 minutes-2 hours, some just via car, some just train, some a combo of train + subway. None were particularly pleasant, as even the shorter drives always involved heavy traffic (thanks, Connecticut).
When I took public transportation I read, surfed the net, or closed my eyes and just rested if the night before was a late one. When I drove, I listened to podcasts or just my iPod. Could not stand the radio.