Most of the bloggers track the so called Page Rank, which is Google's measure of web page authority. The greater this number is - the more authority the page has. The more authority the page has, the more likely it is to show up in the search results for a term contained on that page. However this is not a complete information about a site, as it does not count visits to the site. Much usable measure would be the ranking of actual website traffic which is exactly what Alexa rank was providing.