- Firebug for FireFox, along with other handy extensions
- Visual Studio 2005+, Script Debugger, and/or DebugBar for IE
- JSLint, helps keep your code clean and EMCAScript compliant
- JSON Validator (and formatter), helps make your JSON data more legible
- Aptana, an IDE based on Eclipse with several built-in tools like JSLint to help you avoid simple mistakes.