Developers like to have extensions that make work easier and faster.Here is list of extensions I found very useful-
Visual Studio 2013 has already a lot of HTML/CSS/JS editing features, but Mads Kristensen’s Web Essentials adds even more: zen coding, JSHint, LESS, SASS, CoffeeScript, Markdown, image optimization, intellisense for CSS Media Queries, robots.txt files, HTM5 appcache, AngularJS tags and much more.
Basically an essential extension for anyone doing modern web development using .NET.
Productivity Power Tools
From Microsoft, this extension adds some pretty useful features that help you navigate through the IDE faster. Some duplicates features available in ReSharper, but others are unique. So, install it even if you have it. Check features and download it from the visual studio gallery. And there is also a video that explains the new features.
Not an extension for everyone, but very useful if you do ASP.NET MVC - it explores your solution and visualizes in a tree-like interface all the routes and acts also a routing debugger to help you see which routes are called by specific URLs.
It’s a free product from a software company that commercializes ASP.NET MVC libraries.
Going along with Web Essentials, SideWaffle adds a bunch of project and item templates and snippets for modern web development (and coming also Windows Phone and Windows Store).