I wear wicking t-shirts, which make a big difference compared to wearing cotton Ts. I also keep a few button down shirts in a coat closet to change into. I wash my face in the men's room and bring a fresh towel to dry off. I cool down with a fan on my desk and use a little body powder. By the time my PC is booted up, I feel ready to start my day and have a lite breakfast.
It does get pretty hot/humid around the Philly/Absurdistan border. In addition, we have showers in the gym, but I haven't felt the need to use them...