I usually minimize and surf Digg or Wikipedia. I used to browse PopURLs, but that site can't load on my computer for some reason. I don't know if it's something in the HTML that messes up IE6 -- and, unfortunately, I don't have administrative rights to update software (knowing full well that I would probably kill even more time chatting on Y!).
The good news is that I stay a lot busier during an average work day. We have open enrollment going on, and I juggle my sessions with incoming participants and health evaluations. I conduct sessions with people at the university, and I'm in charge of doing the clinical work for two county-employer groups based out of Pennsylvania. The majority of my clients up north are in their 40s and 50s, and I'm damn impressed with the prevalence of dedicated exercise. Makes me look like all kinds of a slouch.