If you’re using a Mac, and are prone to unhealthy sleeping patterns involving late night computing (like myself), then save your eyes by hitting command-control-option-8 on your keyboard. It’ll invert the screen.
You can also access this from System Preferences –> Universal Access.
Bonus: 25 super ninja night-vision kudos points.

wow cool! that looks pretty awesome.
lol i want some ninja kudos points! maybe i’ll try it on mum’s mac laptop…
Heh – they’re on their way *uses internet skillz to roundhouse kick ninja kudos points to Australia*