gistfile1.txt

server {

        listen   80;
        server_name rtfd.org *.rtfd.org;
        if ($host ~* (.*)\.rtfd\.org) {
          set $slug $1;
          rewrite ^(.*)$ http://$slug.readthedocs.org;
        }
        rewrite ^/(\w+)$ http://$1.readthedocs.org/;
        rewrite ^(.*)$ http://readthedocs.org/;

}