Piwik advertises itself as Open Source Web Analytics - and it seems to be on the right track. It even has an advantage over Google Analytics - live stats! Because having to wait until the end of the day until Google updates Analytics is such a drag ;-)
I just got it running on Gentoo to have a look, tracking stats on Booko. There's a zip file you can down load and install, but I like the convenience of upgrading in place with SCM:
svn co http://dev.piwik.org/svn/tags/0.2.28/ /var/www/stats.mydomain.com/htdocs/
In Gentoo, you'll need to add the following to your /etc/portage/package.use file:
dev-lang/php pdo ctype xml
Then rebuild and give it a day in court.