There are a lot of free http log file analysis tools out there that haven't been updated since the mid 90's, awstats however is both free, and up to date. It looks a bit like web trends (though I haven't used web trends in several years). Here's an online demo. awstats can be used on several web servers including IIS, and Apache. You can either have generate static html files, or run with a perl script in the cgi-bin.
Here's a quick rundown of setting it up on unix/apache
Each virtual web site you want to track stats for should have a file /etc/awstats.sitename.conf the directives for the configuration file can be found here: http://awstats.sourceforge.net/docs/awstats_config.html they also provide a default conf file in cgi-bin/awstats.model.conf you can use this as a base.
Make sure your log files are using NCSA combined format, this is usually done in apache by saying CustomLog /logs/access.log combined you can use other formats but you have to customize the conf file.
You will probably want to edit the LogFile directive to point to where your logfile is stored, SiteDomain this is the main domain for the site, HostAliases lets you put in other domains for the site, and the DirData directive lets you specify where the awstats databases will be stored (each site will have its own file in the directory).
Once that is setup you will want to update the database this is done from the command line by running
perl awstats.pl –config=sitename –update
Now copy everything in the wwwroot folder to a web root, and visit http://sitename.com/cgi-bin/awstats.pl if you want to view other domains use /cgi-bin/awstats.pl?config=othersitename
Where sitename would be the name of your config file awstats.sitename.conf
If you want to generate static html files run the
awstats_buildstaticpages.pl script found in the tools folder. You have to give it the path to the
awstats.pl perl script, and a directory to put the static html files in.
perl awstats_buildstaticpages.pl -config=sitename -awstatsprog=/web/cgi-bin/awstats.pl -dir=/web/stats/sitename/
More setup info can be found here: http://awstats.sourceforge.net/docs/index.html