The Page Strength tool from SEOmoz offers a quick run-down of about 15 or so important metrics to consider when doing SEO. The tool combines each of these elements to figure out an overall strength score for a given URL.
SEOPal is all about ranking the top SEO factors. Everything is created and voted on by the SEOPal community. Here you can learn Whitehat, Blackhat, On-page, Off-page or whatever else suits you best!