- Node.js - Node.js is a platform for easily building fast, scalable network applications.
- ShellJS - Portable Unix shell commands for Node.js
- xpcshell is an XPConnect - enabled shell, sometimes useful for Mozilla development.
- MozRepl - Connect to Firefox and other Mozilla apps, explore and modify them from the inside, while they're running.
- xqjs - Simple console for Firefox.
- Firebug - Developer tools for Firefox, including console.