It's funny how this works, but every mode of ground transport makes you see a different Houston. Cars focus you on the macro—billboards and buildings and such. Buses focus you on your traveling companions or reading / listening material. Walking tends to channel me toward whats on the ground. For a while there when I was a dedicated pedestrian, I was assembling quite the Found-worthy cache.
Cycling kind of offers a melange of all of the above. Here's a few photos to show you what I mean...
