find it here: http://wordpress.org/extend/plugins/simpler-css/
btw. I started a discussion with the plugin author here: http://wordpress.org/support/topic/251057?replies=3
about whether offering one custom css style is enough or if we should go the route this older plugin takes: http://rizapn.blogsome.com/2008/10/19/updated-custom-css-plugin/ and offer one extra stylesheet per theme?
