Lire is hands down the most versatile log analysis software to keep track of in an active network than just webservers available today. Lire not only keeps you informed about your HTTP, FTP, and mail traffic, it also reports on your firewalls, your print servers, and your DNS activity. It is GPL'ed Free Software (and Open Source), built around the idea of extendibility. Its xml-driven reporting engine can theoretically parse any kind of log, given that a service driver is written to convert the raw log into a Lire DLF (Distilled Log Format) file. This means that Lire is also a long-term solution: as new network services come into vogue, Lire will be there to parse and distill their activity for you.
These details are provided for information only. No information here is legal advice and should not be used as such.