Synchronize your external monitor brightness with built-in display. Application reads current brightness of your built-in display and passes it to external monitors via DDC interface. You can adjust brightness by menu in system status bar.
Nocturne is simple app for switching a computer to night vision mode. It has a few tricks up its sleeve: color correction, window shadow toggling, and background removal.
The project has been abandoned. Last version, 2.0.0, released in September 2009, can be still downloaded from Google Code Hosting
Setting the color temp of the screen really only requires about 40 lines of C (80 or so all inclusive). sct is a crude utility which does roughly that. I’d say exactly that, but some of the calculations aren’t actually exact.