Grade Your Website

I came across the Aviva Directory's (http://www.avivadirectory.com/free-online-tests/) listing of 31 free online tools to use for optimizing your website. I am familiar with the web validators but I haven't used the accessibility checkers or page rank stats.

Anyone here use any of these tools?

I've used some of the speed report ones. As far as accessibility goes I like the one that come with the webdeveloper toolbar
http://www.cynthiasays.com/
Seems to be pretty detailed.