The excellent and informative SEOmoz site run by SEO guru Rand Fishkin is re-writing and updating it’s 3 year old ‘Beginners Guide to SEO’. Well worth following if you’d like to brush up on the basics.
Part 1: ‘How Search Engines Operate’ gives an insight into the inner workings of Google, Yahoo, MSN, Ask et al.
Part 2: How People Interact with Search Engines
Part 3: Why Search Engine Marketing is Necessary
Part 4: The Basics of Search-Engine Friendly Design & Development
Part 5: Keyword Research
Part 6: How Usability, User Experience and Content Affect Search Engine Rankings