[cornelln]

Settings > General >Accessibility > Triple-click Home = White/Black

See "White On Black" @ http://www.apple.com/accessibility/iphone/vision.html

SMS looks great when at the movies this way or reading in bed.

[rottencupcakes]

Sadly, it also has the side effect of making the dash and a lot of random apps about 10x brighter.

[madh]

You can also assign a triple-click of the Home button to toggle this feature.