A MIT-licensed template for HTML5 websites that includes a lot of CSS and JS tweaks and optimizations. It provides support for JQuery, Google Analytics, old browsers, etc.
The Aptana IDE is a free, open-source, cross-platform, JavaScript-focused development environment for building Ajax applications. It features code assist on JavaScript, HTML, and CSS languages, FTP/SFTP support and a JavaScript debugger to troubleshoot your code.