Moz (SEOmoz earlier name) is one of the best resource out there on Search Engine Marketing. I have been using them since its earlier days. Rand Fishkin (Founder) is well-known personality in SEO market. I also highly recommend watching Moz's "Whiteboard Friday" video series published every week. It's how I keep myself up-to-date on SEO changes. Here is the direct link to it: http://moz.com/blog/category/whiteboard-friday
