Selective hotlinking prevention through .htaccess
Purpose of this dorky little tutorial
This tutorial describes how to selectively limit hotlinking on your website. You can block hotlinking of most of the images on your website, but allow certain directories to be hotlinked, since this can be useful for you (the website owner).
UPDATE: I’ve published an updated tutorial that improves upon the approach outlined here. I recommend it over this approach. See Preventing image hotlinking: An improved tutorial.