The philosopher Eric Zinn, publicly thinking.
Many [ http://blogs.nature.com/vishal/2010/06/14/the-toilet-philosopher ] have realized that good thinking happens in private, particularly when you don't have anything better to be thinking about. It seems to me that we have only a few such places left: in the shower, on the toilet, and on a bus or train.
It is interesting to note that driving, while not the most demanding task, still engages too much thought to be a good spot for thinking. This is why, even if public transit takes longer, I would recommend that you take it over driving yourself to work.
Similarly, don't read on the toilet, or play music while you shower. Leave yourself alone with your thoughts every now and then, and see where they take you.