Question: What are the various tools to cross-compile or convert Javascript to C# and back? And how to execute JS in C# or C# in JS? 
This is a popular question, and I will provide answers for it.

Answer: 
**Compile C# to Javascript**

* [SharpKit](https://code.google.com/p/sharpkit/) ([site](http://sharpkit.net/)) - Write and debug C# 4.0, compile to JS
* [Blade](https://github.com/vannatech/blade) - Write C# and compile to JS, Interfaces for DOM, HTML, CSS
* [ScriptSharp](http://scriptsharp.com/) - Write C# and compile to JS, jQuery supported
* [Saltarelle](http://www.saltarelle-compiler.com/) - Write C# 5.0 and compile to JS, LINQ, jQuery, NodeJS supported
* [JSIL](http://jsil.org/) - Compile CIL bytecode to human-readable JS
* [JSC](http://jsc.sourceforge.net/) - Compile CIL bytecode to JS, ActionScript, Java, PHP

**Run Javascript in C#**

* [IronJS](https://github.com/fholm/IronJS) - Javascript on CLR/DLR Runtime, Ecmascript 3.0
* [Jint](https://github.com/sebastienros/jint) - Javascript VM, Ecmascript 3.0
* [Jurassic](https://github.com/paulbartrum/jurassic) - Compiles JS into .NET CIL, ECMAScript 3 and ECMAScript 5
* [MS JScript](http://www.west-wind.com/weblog/posts/2007/Feb/14/Evaluating-JavaScript-code-from-C) Engine - Legacy scripting Javascript engine

**Run C# In Javascript**

* [Edge.js](https://github.com/tjanczuk/edge) - Run C# code alongside Node.js, in-process
[JScriptSuite](http://jscriptsuite.com) - compiles MSIL (C# or another .NET language) to JavaScript. Allows debug original .NET (C#) code, provides databind templates, remoting interfaces, controls