If your looking to give your WordPress theme a new design or simply looking to upgrade your code to more modern technologies such as HTML5/CSS3, you will these free WordPress HTML5 frameworks very handy. These HTML5 WordPress frameworks are stripped back bare and mostly include little or no styling which provides a perfect HTML5 framework for you to build your new WordPress site on.
Roots is a starting WordPress theme based on HTML5 Boilerplate, Blueprint CSS (or 960.gs) and Starkers that will help you rapidly create brochure sites and blogs.
Reverie Framework is a versatile HTML5 WordPress framework based on ZURB’s Foundation, a powerful tool for building prototypes on any kind of devices.
Starkers is a bare-bones WordPress theme created to act as a starting point for the theme designer.
Whiteboard is not like most other WordPress Frameworks that include a mess of styles, functions, and content areas that have to be cleaned out for nearly every project, Whiteboard remains a true WordPress Framework.
Bones freely provides you with the option of a responsive WordPress framework or a fixed framework, Bones is a perfect starting point for creating your next HTML5 WordPress site.
Blank is a WordPress theme with all the functionality of a normal WordPress theme but with none of the styling.
The idea is that when starting a new theme, it is far easier to use this as a base then a theme that is already finished and styled.
Handcrafted WP is an almost-naked starter theme that will provide you a rock solid starting point for crafting a serious website on the WordPress platform.
The Brave New World WordPress theme is free from all the elements that are not needed and is built using HTML5, WAI-ARIA landmark roles and hCard and hAtom microformats to provide a great base to build on.
The WordPress Shell provides a great starting point for you to build HTML5 WordPress themes on.
The HTML5 Reset WordPress theme is a blank theme that provides a great empty slate upon which to build your own HTML5-based WordPress themes.
H5 is a semantically sound and fully valid HTML5 framework for which you can build your WordPress theme on.