One of the things that I most enjoy about the stackexchange website is the 'related questions' that show up on the sidebar when I am viewing a question (or show up as I am typing my question). It is readily apparent to me that the logic being used there is much more advanced than 'normal' wp functionality.
I know this would be a very proprietary kind of question, but is there any available documentation on the functions being used to generate the list?
I am looking for something a bit more advanced than simply using tags for relating posts.
*I was going to use YARPP but after reading a number of comments on how that plugin can bring a site to its knees, I figured it would be best to ask first.