I hid the left sidebar and expanded the results column by adding the following snippet to 'userContent.css' in my 'chrome' directory (for Firefox).

    @-moz-document domain(google.com) {
     #leftnav {
      display:none !important;
     }
     #center_col {
         margin-left: 0 !important;
         margin-right: 0 !important;
     }
    }

I think the ads to the right were already hidden by adblock, so you may need to tweak this if you want to preserve ads for some reason.