http://awstats.sourceforge.net/

What is AWStats

AWStats is a free powerful and featureful tool that generates advanced web, ftp or mail server statistics, graphically. This log analyzer works as a CGI or from command line and shows you all possible information your log contains, in few graphical web pages. It uses a partial information file to be able to process large log files, often and quickly. It can analyze log files from IIS (W3C log format), Apache log files (NCSA combined/XLF/ELF log format or common/CLF log format), WebStar and most of all web, proxy, wap, streaming servers, mail servers (and some ftp).
Take a look at this comparison table for an idea on differences between most famous statistics tools (AWStats, Analog, Webalizer,...).
AWStats is a free software distributed under the GNU General Public License. You can have a look at this license chart to know what you can/can't do.
As AWStats works from the command line but also as a CGI, it can work with major web hosting provider that allows CGI and log access.

You can browse AWStats demo (Real-time feature to update stats from web has been disabled on demos) to see a sample of most important information AWStats shows you...