CreativeArt is an awesome free Grunge Theme, that is really a great design, it is widget ready, comes with the psd file. You can download it from here
GrungePress is an eye catching grunge style theme, with a clean 2-column layout, Widget ready sidebar, 3-column separate footer and psd is also provided
MysticGrunge is a Free 2 column grunge WP theme, Widget ready and works with latest wordpress version.
You could download this mystic wordpress theme from here
A Blue Mystic SmartTouch Theme, is a great theme to be used on your blog, decent soothing colors and well rendered blog with a nice pattern background make this theme perfect. Download from here
Scruffy 1.1 is another Free grunge style WP theme. It is Grid based design and layout, built on the popular 960.gs CSS framework. Built upon extensive style sheet with declarations for all areas of the theme. Easy to customize and has widgetized sidebar with styling for all default wordpress widgets. Can be downloaded here.
Our Rights Our Rights is a Grunge style two-column wordpress theme released under GPL. This one also supports widgets.
Duffy is a three-column wordpress theme, grunge style with earthy colors.