F.Lux is a free piece of desktop software that runs on Windows, Mac and Linux (and iOS too). What it claims to do is make your "computer screen look like the room you're in", making your screen seem as if it blends in with the room. This is especially useful if you find looking at a constantly bright monitor in the shy hours of the morning to be uncomfortable.
It's really simple to set up and from what I can see it does what it says. All you need to do is run and install Flux, adjust your location (if it does not pick up automatically for sunrise/set) and then set your interior lighting style (e.g. halogen, fluorescent) for colour accuracy. Flux will do the rest, leave it running and as the outside brightness changes the colour of your monitor will too; creating an automatic brightness adjusting effect.
Flux also includes a bypass mode in case you are up to 'colour sensitive work'.