inside out
I find walking to be a good way to refocus my thoughts at work (and play).
During the warmer months it is a simple matter of walking outside of the office, getting a breath of fresh air. For winter quick walks during the work day I often stay inside. My office (OK, it's a cube!) is in one of a set of two buildings connected by an inside hall. I've discovered that a half of a mile passes under my feet if I walk a loop inside both buildings following the outside edge.