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.