My current Solution for WebPack 2 with Angular 2 for css or scss Loader;
  {
      test: /\.css$/,
      loader: [
          ExtractTextPlugin.extract({ fallbackLoader: "style-loader", loader: 'css-loader' }),
          'to-string-loader',
          'css-loader'
      ],
      exclude: [helpers.root('Content')],
      include: [helpers.root('App')]
  },
  {
      test: /\.scss$/,
      loader: [ExtractTextPlugin.extract({ fallbackLoader: 'style-loader', loader: ['css-loader'] }),
          'to-string-loader',
          'css-loader',
          'sass-loader'
      ],
      exclude: [helpers.root('Content')],
      include: [helpers.root('App')]
  },
Plugins:
  new ExtractTextPlugin({ filename: "[name].css" }),
And now you can use the following in your component
@Component({
   selector: 'logmonitor',
   styleUrls: ['./logmonitor.component.scss', './logmonitor.component.css'],
   templateUrl: './logmonitor.component.html'
})
my current DevDependencies are:
 "devDependencies": {
   "@types/node": "6.0.51",
   "angular2-template-loader": "0.6.0",
   "awesome-typescript-loader": "2.2.4",
   "css-loader": "0.26.1",
   "css-to-string-loader": "0.1.2",
   "file-loader": "0.9.0",
   "url-loader": "0.5.7",
   "html-loader": "0.4.4",
   "svg-url-loader": "1.1.0",
   "less": "2.7.1",
   "less-loader": "2.2.3",
   "node-sass": "3.13.0",
   "sass-loader": "4.0.2",
   "style-loader": "0.13.1",
   "raw-loader": "0.5.1",
   "to-string-loader": "1.1.5",
   "clean-webpack-plugin": "0.1.4",
   "extract-text-webpack-plugin": "2.0.0-beta.4",
   "html-webpack-plugin": "2.21.0",
   "webpack-notifier": "1.4.1",
   "webpack": "2.1.0-beta.27",
   "webpack-dev-middleware": "1.8.4",
   "webpack-dev-server": "2.1.0-beta.12",
   "webpack-md5-hash": "0.0.5",
   "webpack-merge": "0.17.0",
   "typescript": "2.0.10",
   "typings": "2.0.0"
 }
Update 
for Webpack 2.2.1 and extract-text-webpack-plugin 2.0.0-rc.3 here the solution above is not working any more. 
addional devdependencies
"extract-text-webpack-plugin": "2.0.0-rc.3",
"postcss-loader": "1.3.0",
"postcss-import":  "9.1.0",
"autoprefixer": "6.7.2",
"webpack": "2.2.1",
you need to add a postcss.config.js in your root of your app with the content
module.exports = {
    plugins: [
         require('postcss-import')(),
         require('autoprefixer')()
    ]
};
and the new rule for scss is the following
{
    test: /\.scss$/,
    loader: [
        { loader: 'raw-loader' },
        { loader: 'sass-loader', query: { sourceMaps: true } },
        { loader: 'postcss-loader' }
    ],
    exclude: [helpers.root('Content')],
    include: [helpers.root('App')]
 }