Alexa is a good tool to value the sites in the world.
It has toolbar for IE only before. Now Alexa has an addon for Firefox.
Alexa Sparky v1.3.1 for Firefox.
I installed it on my office desktop 5 minutes ago. When I restart the firefox, it redir me to a page with some poll. It ask me following questions.
Gender, Age, Household income, Ethnicity, Education, Children in Household or not, office or home, and post code.
It the status bar of Firefox. There are some new information of the site you are watching. The information includes, Traffic trend, Traffic rank, Reach meter.
When I read this blog’s site information provided by Alexa, I think it is a very helpful tool for blogger to optimize the content. And know more about the readers of the blog.