Google's SEO Starter Guide is a good place to start: http://static.googleusercontent.com/media/www.google.com/en/...

Another is their SEO Report Card from a different angle: http://googlewebmastercentral.blogspot.com/2010/03/googles-s...

Moz (SEOmoz) provides another good source of info here: http://moz.com/beginners-guide-to-seo