Sometimes we need a new pair of glasses a site – whether the site is our own, a competitor’s, or a possible new client site. SEO tools like link checkers, html validators, speed checkers, and spider simulators can lend a new perspective on a site’s performance, highlighting its strengths and weaknesses.
This WhoIs Tool gives a lot more information than your average whois:
http://whois.domaintools.com/. You can see the registry and IP history, for example. The Site Profile tab assesses relevance scores on meta data and shows any listings in DMOZ or Yahoo. It offers information on similar domains. There’s a thumbnail of the site and there is also a link to a wiki for the subject website on aboutus.org.