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.
Splunk is simply unmatched as a security log analysis tool. Grab traps, alerts, and syslog and SNMP data, and once you have the data, Splunk lets you graph and search it quickly via a simple, browser-like interface. In addition to helping you spot potential threats and dangerous trends, Splunk can aid compliance efforts, get alerts on thresholds you set, and generate nice reports of your findings.