All,
Everybody knows about Google Analytics and StatCounter for website analysis but here is another open source web analytic add into your analytic list:
Piwik
Piwik is a downloadable, open source (GPL licensed) real time web analytics software program. It provides you with detailed reports on your website visitors: the search engines and keywords they used, the language they speak, your popular pages… and so much more
Code:piwik.org