Create a standing computer desk, or use an existing surface to compute and surf the net from a standing position. You will burn more calories, exercise posture muscles and, in general, promote better health than doing it sitting all the time.
I created my standing computer station without spending a cent. I put an old monitor and keyboard on top of my dresser drawers which were just the right height. I have a slightly old laptop which serves as CPU. I haven't completely abandoned my regular computer desk. I switch between the two.