http://www.evanmiller.org/how-not-to-sort-by-average-rating....
and this little page demonstrates an adaptation to a 5-star rating system:
http://www.goproblems.com/test/wilson/wilson.php?v1=0&v2...
Randall Munroe gave a user-oriented explanation of the system here:
http://blog.reddit.com/2009/10/reddits-new-comment-sorting-s...