Bootstrap Made offers free Bootstrap templates. They specialize in creating elegant, clean and beautiful free website templates using the Bootstrap framework.
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.
Colorlib offers some of the best free WordPress themes, responsive and full of options, ranging from business themes to blogs and portfolios.