Coco A CoffeeScript dialect that aims to be more radical and practical, also acts as a test bed for features that get imported in CoffeeScript.
LiveScript is a fork of Coco that is much more compatible with CoffeeScript, more functional, and with more features.
IcedCoffeeScript A CoffeeScript dialect that adds support for await and defer keywords which simplify async control flow.
Parsec CoffeeScript CS based on parser combinators. The project's aim is to add static metaprogramming (i.e. macros + syntax extensibility) to Coffee Script (CS), similar to how Metalua adds such features to Lua. The resulting compiler, once merged with the official compiler, should be usable as a drop-in replacement for it.
Contracts.coffee A dialect of CoffeeScript that adds built-in support for contracts.
Uberscript, a CoffeeScript fork that adds type annotations which are compiled to Google closure compiler type annotation comments.
ToffeeScript A dialect of CoffeeScript that support Asynchronous Syntax and Regexp operator =~
Caffeine A dialect of CoffeeScript that support packages and classes import, useful for browser applications
heap.coffee A dialect of CoffeeScript that offers a C-like type system with manual memory management
Kal makes asynchronous programming easy and clean by allowing functions to pause and wait for I/O, replacing an awkward callback syntax with a clean, simple syntax
promiseLand promiseLand is a very promising Language. It includes ES5 strict mode, uses the * dereferencing operator to access promise results and introduces additional features designed to let you focus on your program logic. Such as dynamic typesafety, frame addressing, generic load and safe features.
Rusthon Integrates several python to js methods into one project. Very Active. Not only for JS & Py, but also Go, C, Nim, etc.
Spiderbasic [commercial] SpiderBasic is new web client-side programming language based on established BASIC rules. Its main purpose is to allow development of very complex, windowed based web applications. It provides a large commandset to handle complex and reactive GUI, 2D games, and many more in a coherent manner.
Haxe compiles to several platforms (C++, Flash, JS, Neko, PHP, Java, C#, Python).
Fantom Evolutionary object-oriented language emphasizing succinct and effective APIs (JVM, CLR, JS).
SpiderMonkey Parser API - see also reflect.js above. The AST interface specification is succeeded by the ESTree specification effort.
ESTree Specification - An effort to better standardize an AST specification based on the original Spidermonkey Parser API. It is used by Acorn, Esprima, and SpiderMonkey's own parser. This succeeds the original SpiderMonkey Parser API's AST specification.