Glen Akins has written an article detailing his USB-connected big red button project:
In this project, I mount the electronics from my single-key USB keyboard project to the back of an industrial mushroom push button switch. The finished big red button now activates my screensaver with a single overly-large button press. The biggest issues in this project were where to mount the USB electronics and how to connect the USB cable between the button and my computer.
More details on Photons, Electrons, and Dirt blog.