To often you are unable to really utilize an SEO tool found on Google, they may require your contact information, only run once then require a subscription, most seem to be more a sales tool than an SEO Tool. Here are some tools that I find useful and that minimize the bull crap that can come with the most popular SEO sites.
Just a few of the tools available…
Domain Authority Checker – Domain authority represents how authoritative a website is on a scale of 0-100. It is calculated by Moz, an SEO software provider. The score is largely based on the quality of links going to a website, as well as the MozTrust and MozRank scores.
I want to remind everyone that the url you type technically is a completely different site so as you see in the comparison of multiple addresses that lead to the same site there is variation.
My personal site will rank low … it is very new.
Moz Free Tools – several tools, requires registration then limited to 10 queries a day or so.
And finally I want to say check out Ultimate SEO. Its a great site.