iv / lv5 is a new ECMAScript engine written in C++, that conforms ECMA262 5.1 specification completely.
It includes ECMAScript lexer, parser, RegisterVM, baseline JIT compiler for x86_64.
The ecosystem composed of these tools is described in this paper.
escope is an ECMAScript scope analyzer. It accepts AST and analyze scope and variable information.
doctrine is a JSDoc parser with complete Type annotation support. It is used in Eclipse Orion's JSDoc support.
Taberareloo is a Google Chrome extension to support cross posting to many social services