Requires only a small button on the tracked pages. Tons of statistics about your traffic. You may opt to earn revenue by displaying a larger, paid banner ad. Private or public stats. This tracker allows you to track multiple pages and gives very detailed reports including keywords used to find your site, referrers, plugins your visitors have and plenty more.
Small banner is added to the pages tracked.
Another free webpage tracker that gives rather complete statistics, including referring links, browser version and a lot more. Stat Track Free private or public website statistics, tracks the last 20 referrers, top 20 referrers, visitors for the last month and lots more. Just a small 88x31 pixel button added to your page. The other is their Out-Tracker that tracks clicks on your external links and download files. Sitegauge Lots of info about your visitors, including referring urls, keywords used, multiple page tracking, private stats, and just a small button.