Perhaps this is common knowledge, but I just figured it out (accidentally) and its pretty damn awesome! If you maintain a regular .js file, and then create a copy of it .min.js with a compressed copy of your code, Visual Studio will maintain that minified version automatically whenever you make changes to your original! It will create a .map file that it uses to keep track of the differences between your source and minified versions (variable names, etc). Whenever you make an edit to your regular .js file, those changes will be reflected in the .min version!
For those of us using basic one-off files and don’t want to deal with bundling (or aren’t using .net 4.5 yet) this is pretty handy!
Note: This is most likely the result of the Web Essentials plugin and not Visual Studio itself. It was brought to my attention that using Web Essentials, you can also minify and bundle your js and css files (via right click menus)!