Here are List of best Free WordPress Themes or Templates on net, some of them are premium quality free wordpress themes.
15 High Quality Premium-Like Free WordPress Themes
15 Free Premium-like WordPress Themes from Noupe
100 Excellent Free WordPress Themes
Awesome 100 free high-quality WordPress themes from Smashing Magazine,
83 Beautiful WordPress Themes
83 free WordPress Themes you probably haven’t seen yet. All themes offer quality, elegance and a user-friendly interface from Smashing Magazine,
30 Free High Quality WordPress Themes
In this article they present over 30 fresh free high-quality WordPress themes. All themes can be downloaded, customized and used for free — in personal or/and commercial projects.
WPThemesPlugin
Great Collection of Free WordPress Themes and Plugins
Free WordPress templates and themes
Another Greate Collection of Free WordPress themes
Free WordPress templates
Nice Collection of Free WordPress themes
Oh, I would suggest adding http://new-wordpress-themes.net