It would be very useful to retain visitors on the site to design a RelatedPosts system that would also be easy to use by the webmasters. I propose the following solution: define keywords for each post through the Keywords plug or another similar, and show a short list of posts with similar keywords. I think it would be a nice way to do it, but I really have no idea on writing PHP, so I hope someone who can will also find it useful and do it.