SASS has become more and more vital to the sites I write code for both at home for personal projects, and at work for the business applications we write. If you don’t know what SASS is yet, you should really do yourself a favor and read up on it, but basically it’s a language that allows you to write better and more organized CSS which then complies to standard CSS which can be served to the browser.
At home on my Mac I’ve been using the terrific CodeKit ($25), which just runs in the background, watches my project folders, and generates CSS files whenever I save my SASS (and LESS, CoffeeScript, etc.). However, at work we run Windows and use Visual Studio as our IDE for which the “perfect” integrated solution doesn’t really exist yet.
Here are the current possibilities:

Chirpy is a pretty handy little Visual Studio extension that can handle basic SASS compilation. We use it at work, but only for one of it’s other features: JavaScript compression for files named *.chirp.js
.
It’s SASS features seem fairly limited since you can’t @import
other SASS files, it has no syntax highlighting support (to my knowledge), and it does’t give any error message when it fails to compile. Maybe I’m missing something basic, but without these features it just won’t work for how we need to use it.
I hate making the other developers I work with have “required” plugins, but right now this is the easiest way to compress our javascript files when we edit them until we can work it out to upgrade to .NET 4.5 and use the new bundles. As for SASS integration, I’d recommend skipping Chirpy for now.

Mindscape is another neat little Visual Studio extension that has a bunch of features, but again we only make use of one of them. It has terrific SASS support for all the features we need, and heck it even supports Compass too! It’s great and all but when using the free version it becomes slightly annoying since it disables basic features like the ability to comment/uncomment lines of code with a key command. It’s probably the most ridiculous feature could take away from you until you pay for it. A coworker of mine bought a pro license ($39) for himself at home, but then found out that it’s only good for one year. It’s a good tool, but it practically requires a per-developer yearly subscription to be great.
It works for now, but if something better comes along I’d be happy to ditch Mindscape. If you need to use SASS in Visual Studio, this is probably the best option right now.
Future Possibilities:
The Visual Studio Web Essentials extension gives you lot of new experimental features. Once these features mature, they are moved into the fully supported Web Tools extension. If you want to stay on the cutting edge you can install Web Essentials, otherwise just install Web Tools for a bunch of great new features.
The newest version of Web Tools added native support for the LESS CSS dynamic stylesheet language. It has full syntax highlighting, compilation to CSS, and a pretty nifty editor window as well. LESS is well thought out language that is somewhat popular, but after considering converting all my code from SASS to LESS it became apparent that SASS just has more features, is more extensible, and is generally more widely used.
The Web Essentials site has a page where you can vote for the desired features in the next version, and one of the most popular items is to add support for SASS/SCSS. Since this ticket was opened in September of 2012, they’ve added syntax highlighting support which is nice… but it’s rather useless since it doesn’t actually do the essential step of compiling to actual CSS code. A site admin has since said that the prototyping phase for real SASS support has been started, so I feel there is a decent amount of hope that native SASS support will be coming to Visual Studio in the near future!
I’m venturing a guess that they decided to go for supporting LESS first since it has fewer features and a compiler written in .NET – low hanging fruit. The compiler for SASS is written in Ruby, so that’s a bit more complicated to add onto Visual Studio since it’s a completely different language. Hopefully (if possible) a real .NET compiler can be used (they do exist) and Visual Studio will then have true support for the two major dynamic CSS languages.
My only annoyance right now is that when both Mindscape and Web Essentials are installed, they both fight for syntax highlighting and you can occasionally get some strange looking code. The only solution for the time being is to pick one and disable/uninstall it. Hopefully this can be fixed by one of these vendors in a forthcoming release.