For a better working experience in Visual Studio, you could install the last version of Web Essential which is starting to support Sass (SCSS syntax).
Alternatively you could install Sassy Studio or Web Workbench.
Then to compile your .sass/.scss files in your ASP.NET project, there is some different tools: via Web Essential, Web Workbench, SassC, Sass.Net, Compass, SassAndCoffee...
Web Essential a fully featured plugin for Visual Studio, which really give a better experience for all Front-End stuffs. The latest version is starting to support Sass (SCSS syntax). Internally it use the Libsass to compile the SCSS to CSS.
Web Workbench is another plugin for Visual Studio that add syntax highlighting, intellisence and some other useful stuff for editing SCSS files. It can also compile your code into normal or minified CSS. Internally it used a wrapped version of the Ruby Sass compiler.
Sassy Studio: another plugin for Visual Studio. Less featured but much lighter.
answered 2012-01-24T03:49:44.317