The Art Of 'Goldilocks' SEO
I always pay attention to Aaron Wall, who runs SEOBook, because he is always on the money. He is one of the very few Google Watchers that is consistently insightful and isn't afraid of writing hard hitting articles critical of Google -- if it's called for.
Here is one of his latest infographics, and again, he is spot on about the changing trends in how Google views the web. It's shocking how much valuable advice he gives away: