Ever woken up early, gone to your computer, and switched on the monitor only to be blinded? I sure have. And recent research shows that too much blue light (LCD panels are very blue) in the evening can actually impact your sleep as well.
F.lux is a free utility that automatically changes the color temperature of your screen as the sun sets. You give it your latitude and longitude (if you don't know, you can look it up by zip code), and as it begins to get dark the program will turn your screen redder. At first it looks really weird, but once you get used to it it's significantly more comfortable to use your computer. If you ever use your computer after about seven o'clock or so, you should give f.lux a try.
Sound good? You can download f.lux here. Installation is super-simple: just run the setup file and then click the new icon in the system tray next to your clock to set your location and other settings.