AWStats is short for Advanced Web Statistics. It's a free 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 that your logs contain, in a 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, and streaming servers (and FTP
servers or mail logs).

WWW: http://www.awstats.org/