After the last front page thread about HN ranking (https://news.ycombinator.com/item?id=6799854) I built http://news-yc.appspot.com, which shows an unpenalized version of the front page (and tries to calculate the applied penalties). My plan, time permitting, is to start clustering submissions by topic (probably using k-means or similar) as well as building a recommendation engine around submission comments ("users who commented on this submission also commented on…").