Wow, I've got to hand it to Google – again – for offering an extraordinary application at no charge. Google Analytics was formerly "Urchin", and cost about $500 monthly. It's an extremely robust log analysis tool that allows detailed "drill down" examination of things like referrer logs, page views, and much more. A very clever user friendly tool called "site overlay" allows you to explore the click through rates of a home page's (any page's?) internal links. Very helpful in designing navigation for the site.