For me, it is when I run. Not that He doesn't reveal Himself in other ways and not that I only contemplate His glory when I run, but there is something about running that is so incredible. God designed my body to be able to persevere and push through 1, 2, 3, and 8 miles. He made my muscles strengthen and gave my lungs the capacity to fill and empty as I take each step. The fact that my body responds to the activity is amazing to me. Everything changes. Weight, muscle mass, the percentage of fat, etc.
I love that God is a God of detail. I love that He made my body to work the way that it does on purpose. He knew exactly what He was doing. I love that He created a beautiful world for me to observe while I am running (and an iPod to listen to courtesy of Anthony).
I want to be better about meditating on God's awesomeness. It is what we (I) are (am) called, as Christians, to do.
Psalm 143:5
I remember the days of long ago; I meditate on all your works and consider what your hands have done.