I have found two sites that are useful for bloggers.
One is the http://ppp.customtools.urltrends.com/index.php. This is where PayPerPost checks the Google Page Ranks and the Alexa Ranks of its Posties.
The other is http://www.mikes-marketing-tools.com/ranking-reports/. If you want to check the search engine ranking of a certain keyword in your website or blog, this is the site for you. Just enter your main URL and the keyword/s, submit and you would the rankings in different search engines - Google, Yahoo! Search, AOL, MSN, AllTheWeb, and AltaVista; and in Web Directories: Yahoo! Directory & Open Directory (Dmoz).