- Alexa.com — A free service that estimates site traffic over a three-month period. The numbers are compiled from the Alexa Toolbar that’s installed on the millions of users’ browsers. This information can be used to gauge a site’s overall online ranking by combining a measure of its current reach and monthly page views. This reach is determined by the number of Alexa users who visit the site daily. The site with the highest combination of users and pageviews is ranked highest. You can use Alexa to see how your site rates compared to the competition. Alexa also provides information on incoming links and traffic trends over time.
- Compete.com — provides free tools and data to compare two or more sites for monthly traffic, specific site keywords, overall online reach, US audience share, current promotions, and many other competitive data points.