Background: anything light, and the text dark.
I don't mind headers and menus in white or light text on dark or black background, but for body text I find dark on light easier to read.

Definitely NOT any mixture of medium tones.
This sort of thing or this REALLY hurts your eyes! (ouch - sorry!)

Graphics make nice backgrounds too. Either colour gradients or pictures, but lighten and blur them - like the one I used here where the text is over a very pale tileable blur of the picture which I use as text background everywhere on that site.

Anahata