I've got to put a vote in for white backgrounds. I find dark background terribly hard to read, especially with colored text. White backgrounds have a higher contrast with the text. I also turn the brightness down on my monitors, so I don't feel it's too blinding.

I also can't stand it if the syntax highlighting is too colorful. I like some coloring for reserved words, type names, comments, and string literals. Other than that black on white.

What I find more important that color schemes is having a nice font. If you're on Windows, and not using Consolas, you're missing out big time. Consolas is actually designed to look good with sub-pixel rendering. If you can't use Consolas, Bitstream Vera Sans Mono is a nice second.