HTML5 Up
HTML5 Up makes spiffy HTML5 site templates that are responsive, built on HTML5 + CSS3, super customizable and 100% free under the Creative Commons license.
Related Tools
Just Free Themes
Just Free Themes offer over 1,000+ awesome, pixel perfect and free WordPress Themes, ranging from eCommerce to blogging to fashion and more.
Bootstrap Made
Bootstrap Made offers free Bootstrap templates. They specialize in creating elegant, clean and beautiful free website templates using the Bootstrap framework.
Share Bootstrap
Share bootstrap offers great free themes and templates built with Bootstrap. It is an especially great resource for Dashboard templates and themes.
Templated
Templated is a collection of over 800+ simple CSS, HTML5 & responsive website templates, built and released for free under the Creative Commons.