SquishIt

SquishIt is an asset optimization library for .net web applications. It handles combining and minifying css and javascript assets through creation of bundles. There are currently extensions available that allow use of .less, coffeescript, SASS/SCSS and Hogan templates through SquishIt's preprocessor pipeline. There is also an extension that writes your combined files to Amazon S3 that can serve as a template for integrating with the CDN of your choosing.

Bundler

Compile & Minify Less/Sass/Stylus/Css/JS/CoffeeScript/LiveScript files. Integrates with MVC and ServiceStack

Bundle Transformer

Bundle Transformer - a modular extension for the System.Web.Optimization (also known as the Microsoft ASP.NET Web Optimization Framework). StyleTransformer and ScriptTransformer classes, included in the core of Bundle Transformer and implement the IBundleTransform interface. They are intended to replace the standard classes: CssMinify and JsMinify.

NodeAssets

Asset Manager for .NET that has live CSS updates using SignalR and can optionally leverage Node.js compilers

Cassette

Manages .NET web application assets (scripts, css and templates)