I have a software recommendation. Nocturne has been around for a while and what it does is invert your desktop. I know, ctrl+option+command+8 will do that too, but this gives you more control over the inversion and adjusts tones and subtle stuff. My eyes hurt from staring at the screen for a long time, plus I am nostalgic for the old Mac SE simple monochrome desktop, so this is perfect. It can even be set to respond to the light meter built into my fancy, way too expensive notebook. A darker screen uses less power, which is the idea behind sites like Blackle.com and you get a lower bill or better battery life. I thought I would get sick of it by now, but in low light conditions I prefer the mild sepia tone.
Its free from the genius of Quicksilver fame, the launcher that launched launchers. No one else has even come close to the awesomeness of Quicksilver though. Go get some Goth for your desktop! It's free!
