http://mattmcvicker.com/45-creative-portfolio-wordpress-themes/

http://www.smashingapps.com/2013/01/14/44-powerful-yet-free-wordpress-portfolio-themes.html

http://themesyard.com/workality-free-portfolio-wordpress-theme/

http://ginva.com/2012/02/123-free-clean-and-simple-wordpress-themes/