Free SEO tool to estimate traffic

Check out www.statbrain.com, a free tool to estimate the amount of traffic a web site gets.

Statbrain estimates the number of visits that a website has based
on offsite factors like backlinks, Alexa Rank etc. Statbrain does
not have access to log files or any counter information.

The number of visits that Statbrain estimates gives you an idea of
the number of visitors that a website has, but not the exact
visitor number.