AWStats is a free powerful and featureful tool that generates advanced web (but also ftp or mail) serverstatistic, graphically. This log analyzer works as a CGI or from command line and shows you all possible information your log contain, in few graphical web pages like visit, unique vistor, authenticated user, page, domains/countrie, OS busiest time, robot visit, type of file, 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 file, 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 server, plugins and a lot of features.