Drupal equivalent of Starkers
If you're looking for clean and easy base themes, there's Stark (which has a contrib version, as well as the version in Drupal core)


  This contrib version of Stark is an exact copy of the one in Drupal 7
  core with one exception. This version now uses a responsive design that matches a Drupal 8 proposal to make Stark use a responsive layout.


There's also Mothership, which I've never used - but it looks pretty awesome!


  The Mothership is a HTML5 base theme that offers a workaround to
  Drupal’s obscure love for wrapping everything in 2 divs and slapping
  on 3 CSS classes wherever possible.