Google Analytics
Google Analytics is a product from … Google of course. It might not be the most accurate of all traffic-tools for websites, but it certainly is the cheapest solution : it’s for free!
Google Analytics will measure : visits, pageviews, origin of visitors, keywords, and so much more. It offers and endless number of reports that can be viewed from different perspectives. On top of that, you can integrate Analytics into your E-commerce. This way you can keep track of your sales and enjoy the additional reportings.
Thank you Google!