The Webalizer is a fast, free web server log
file analysis program. It produces highly detailed, easily
configurable usage reports in HTML format, for viewing with
a standard web browser.

Modlogan is a modular logfile analyzer which is
currently able to parse ftp-, webserver and squid logs. The
generated output can be viewed by a webbrowser (->moglogan,
webalizer) or your favorite text editor (->text). The
template engine allows you to create the output with your
prefered look and feel.

AWStats is a free powerful and
featureful tool that generates advanced web, streaming, 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 all major server tools like Apache log files
(NCSA combined/XLF/ELF log format or common/CLF log format),
WebStar, IIS (W3C log format) and a lot of other web, proxy,
wap, streaming servers, mail servers and some ftp servers.
Urchin Software from Google analyzes traffic for one or more
websites and provides easy-to-understand reports on your
visitors - where they come from, how they use your site,
what converts them into customers, and much more. If you
have content behind a security firewall or on an intranet or
internal network that prevents you from using the Google
Analytics service, Urchin Software from Google is for you.