AWStats is a free powerful and featureful tool that generates advanced web (but also 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 like visits, unique vistors, authenticated users, pages, domains/countries, OS busiest times, robot visits, type of files, search engines/keywords used, visits duration, screen size, HTTP errors and more...
Statistics can be updated from a browser or your scheduler.
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 (and ftp servers or mail logs).
The program also supports virtual servers, plugins and a lot of features.