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