Search Engine Ranking Factors
http://www.seomoz.org/article/search-ranking-factors

SEOmoz
2008

Abstract:

This document represents the collective wisdom of 37 leaders in the world of organic search engine optimization. Together, they have voted on the various factors that are estimated to comprise Google's ranking algorithm (the method by which the search engine orders results). The result is a resource of incredible value - although not every one of the estimated 200+ ranking elements are included, it is my opinion that 90-95% of the knowledge required about Google's algorithm is contained below.