By Michael Yoshitaka Erlewine (http://mitcho.com/)

Yet Another Related Posts Plugin (YARPP) helps your readers and the search engine bots to find other posts on your website that are similar to the one they are currently reading.

Once installed and activated, the YARPP plugin is virtually done. Check out one of your blog posts, and see if you like the results. Below the article will be a list of similar posts to the one you're reading. While out of the box YARPP will satisfy 80 percent of the people, you should check out the YARPP settings, as it offers a ton of configuration options.