Having that software itch again I just had to get my display brightness turned down on my Apple Cinema Display. It's a wonderful piece of equipment, but it has no external controls to manipulate brightness. Just a soft-key that when touched flashes. When connected to a mac this key launches their display config tool so you can tweak the brightness, but on Windows and Linux, it does nothing.
Therefore, I wrote a little tool called acdctl which stands for Apple Cinema Display Control (or controller). It enables me to manipulate the brightness of the display via the command-line. Sure there's no fancy slider, but it's all I really need to push things down a little. I learned a bit more about programming with libusb and otherwise had a good time writing it. Even though USB is a crap protocol for bulk storage (imho), it's excellent for these sorts of light data, high diversity applications. Now that I have it, I wish I could use something like it on my CRT displays.