Responsive Themes
Attitude
http://www.themehorse.com/themes/attitude/
Demo
http://themehorse.com/preview/attitude/
Expound
Download
https://wordpress.org/support/theme/expound
Demo
http://expounddemo.wordpress.com/
Thematic
https://wordpress.org/themes/thematic
Demo
http://demo.thematictheme.com
skeleton
Simple responisve Theme
http://themes.simplethemes.com/skeleton
https://wordpress.org/themes/smpl-skeleton
Newzeo
http://wpthemedownload.org/newzeo/
Codium & Codium Extend
http://codium.code-2-reduction.fr/
http://codiumextend.code-2-reduction.fr/
Links
http://t3n.de/news/kostenlose-wordpress-themes-responsive-webdesign-376838/