http://awstats.sourceforge.net/

AWStats is a free feature rich log analyzer tool which generates statistical reports from your ftp log files, server logs or mail log files. This tool is a real time log analyzer which supports has the capability of processing log files quickly from servers like apache, webstar, IIS and many more.

• Total number of visits and unique visitors
• Time spent by visitors and their last visits
• Visits from different country and hosts
• Operating system used
• Internet Browsers and their support ratio
• Robot visits detail
• Most views pages
• Entry and exit
• Visits from authenticated users
• List of hosts and unresolved IP addresses
• Visits of robots
• Search engine keywords
• Http Errors