Some resources for finding out how many visits a website receives include Google AdPlanner and Alexa. Google Analytics and Yahoo Web Analytics offer free services for website owners interested in learning about traffic at their websites. Other tools for finding visits to a website include Compete, BizInformation and Quantcast.
Google AdPlanner mainly targets advertisers deciding if it is worthwhile to advertise on a particular site. It allows users to break down the numbers to look at the traffic from a particular country. Amazon.com owns Alexa, which offers a wealth of stats about websites.
Compete has some limitations on finding information if the user doesn't have a pro account, but it offers graphs charting a website's course. BizInformation shows the number of visitors as well as what the site is worth. Quantcast allows the user to break down the stats by time period as well as see the demographics of the visitors, such as sex, age and income.
Google Analytics is a popular tool, and about half of the top websites in the world utilize it. It allows the website owner to track things such as how visitors were referred to the site, how often they visit and other specific information.