Share bootstrap offers great free themes and templates built with Bootstrap. It is an especially great resource for Dashboard templates and themes.
Colorlib offers some of the best free WordPress themes, responsive and full of options, ranging from business themes to blogs and portfolios.
Bootstrap Made offers free Bootstrap templates. They specialize in creating elegant, clean and beautiful free website templates using the Bootstrap framework.
Templated is a collection of over 800+ simple CSS, HTML5 & responsive website templates, built and released for free under the Creative Commons.
HTML5 Up makes spiffy HTML5 site templates that are responsive, built on HTML5 + CSS3, super customizable and 100% free under the Creative Commons license.