Black / Blue Visual Studio 2010 + ReSharper 5 Theme
I have been using black background in Visual Studio for as long I can remember. I started out using Rob Conery's black / orange TextMate theme, but last year I created my own black theme with a blueish style. Today at the ANUG code dojo we tweaked it to actually look alright with the changes in Visual Studio and especially ReSharper.
You can download the theme here if you want a nice black theme.
It looks like this:
Subtle highlights of active identifier: