Zeldman's recent redesign was a little controversial for some. The colour scheme meant that laptop users (with their silly LCD screens) were having difficulty reading the text. He "fixed" it with a stylesheet switcher which gave access to a high contrast version.
Over at Superfluous Banter, they've been talking about using shades of dark gray instead of black when you've got a light coloured background. And then they put a little more thought into in, have linked to these examples of contrast comparison and opened their comments to opinions. Some of the new stylish CSS sites are falling down on this very issue - using washed out, mellow colours which do nothing for readability.