A pretty well done infographic covering SEO. Every client of mine should see this (be sure to click through to the full sized image):
http://www.datadial.net/blog/index.php/2010/04/13/seo-in-pictures-our-seo-infographic/
The image covers everything from basic keyword research concepts, through site architecture, page optimization, link building, SEO tactics, social media, and some basic SEO and PPC clickthrough stats and explanations.