I just switched my blog's theme to [Vigilance](http://thethemefoundry.com/vigilance/) (after using Thesis for awhile). I've hacked Vigilance a bit, to make the content area wider, and nuke the sidebar (well, really the sidebar just displays underneath the content div) and a few other things (like telling it not to show the author - I'm the only person that posts here - and turning off some of the comment-specific logic and display.
Doesn't get much more minimal than this. No banner images. No sidebars. Wide content. No fuss. Exactly what I want.