Every year for the past six years (I think), SEOmoz has provided a thoroughly researched data set called “Search Engine Ranking Factors”. The data is gathered through their own research and through surveys from SEOs and others in the online advertising and search marketing fields.
It’s a fantastic resource for SEOs, data junkies, or simply for those interested in how or why search engines show the results they do. This research always provides solid, actionable data, which is hard to find these days, much less for free.
Anyways, the report is released around June of each year, so I’m a tad late with talking about it. Still, the information it contains should be referred to again and again, so I don’t feel so bad.