AizeMashu via the MAKE Flickr blog made the coolest OS switch (literally). “I bought a generic electrical switch from Radio Shack and wired it to switch my computer OS between Linux (left,) Windows (right) and boot disc (the off setting.) To get an idea of how macro this image is, the switch is mounted on a 3.5″ external drive plastic knockout”. Link.
Homemade Linux Windows Hard Drive Switch