There has been a lot of talk recently about HTML5 and with the W3C's release of the HTML5 logo interest has grown on a much larger and global scale. For designers and developers alike there is no time like the present to start using HTML5, even if it is just your personal weekend project, the reality is sooner or later clients and the web alike will make the shift.
Now where do we stand from a Drupal starter theme perspective? If you have no clue on where to begin in regards to HTML5 and if you are looking for a Drupal starter theme to get the ball rolling you are in luck. The Drupal community has been actively developing starter themes and sub themes with HTML5 & semantic markup in mind.
The first theme we would like to highlight is Boron. What Boron does is convert the core template files to HTML5 markup and also comes with a neat feature that utilizes semantic elements. The neat part about Boron is that it is also ships as a Zen sub-theme. This is especially useful for those who are familiar with the Zen framework and would rather work with a sub-theme than utilizing a base theme. Boron is available for both Drupal 6 and Drupal 7.
Known to be a highly configurable and flexible starter theme AdaptiveTheme, like Boron, is structured around the use of HTML5 and semantic code. AdaptiveTheme also comes with a few features out of the box that makes configuring layouts and creating sub-themes easier.However, if you are looking for an HTML5 version for Drupal 6 you are out of luck as the HTML5 version is only available in Drupal 7.
Under active development the HTML5 Base is another theme to watch. At the present time (date of this article) there has yet to be an official Drupal 7 release. All is not lost though, if you are comfortable in up-to-date code or would like to contribute you can test the development release for either Drupal 6 or Drupal 7.
If you are not into Drupal starter themes, or if you are of those who prefer to create themes from scratch; but still want to be involved with HTML5 and Drupal, I suggest looking into the HTML5 tools project. The goal with this module is to focus on semantic markup as well as implement HTML5 elements. Currently the focus is on XHTML overrides in Drupal 6 but there is also a development version available for Drupal 7 that is worth checking out.
In summary if you are looking to dive into HTML5 markup in the near future we have highlighted a few starting points. For a personal pick I would go with the Boron module as it has both a Drupal 6 and Drupal 7 version, not to mention Boron for Zen which is an HTML5 Zen sub-theme.
Update - October 7 2011:
Additional drupal html5 themes added since the recent post: