Shades - Shades is a FREE utility for controlling the brightness of your screen.
Simple Screen Shade - Description and screenshots of Simple Screen Shade.
myPoint Shade - Stop burning your eyes! myPoint Shade is caring for your eyes' comfort.
ScreenDimmer - Having two monitors on OSX is both a joy and a pain.
Nocturne - Nocturne is simple app for switching a computer to night vision mode.
Dimmer - A very small and free utility for Windows to reduce brightness on LCD/TFT screens.