Directory listing can be enabled (disabled by default) by adding this:

autoindex on;

Example usage

http{
   server {
     #Server with no Directory listing
     listen 80
   }
   server {
      #Server with Directory listing
      autoindex on;
      listen 8080
   }
}

Original [source][] [source]: http://justinbkay.org/2007/12/23/nginx-enable-directory-listing