1. This is a great article from Search Engine Land outlines some of the things you can do with your Google webmaster tools which can help with your SEO.
http://searchengineland.com/9-step-seo-checkup-using-google-webmaster-tools-57061
2. While technically not an article what Search Engineland has created in this periodic table of the elements for SEO ranking factors is pretty amazing and worth a study.
As they say on it “Search engine optimization — SEO — seems likes alchemy to the uninitiated. But there’s a science to it. Search engines reward pages with the right combination of ranking factors. ” This article from may help you to understand it better.
And to round out my list of 5 the last 3 are from SEOMOZ.org
3.The Seomoz social media checklist is not for total newbies but still worth a read by anyone interested in this aspect of SEO. http://www.seomoz.org/blog/the-social-media-marketers-seo-checklist
4. Another great article about the SEO favorite Title tag
http://www.seomoz.org/learn-seo/title-tag
5. And finally a read on the use of the meta description tag -http://www.seomoz.org/learn-seo/meta-description