W3C Markup Validation Service, a free service that checks Web documents in formats like HTML and XHTML for conformance to W3C Recommendations and other standards.
“For people who make websites” A List Apart Magazine explores the design, development, and meaning of web content, with a special focus on techniques and benefits of designing with web standards.
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.
MIT-licensed HTML5 template and CSS framework built for responsive design based on a 12-column grid. The boilerplate contains no JavaScript, just HTML, CSS and example site icons (favicon & iOS).